The Migrations of Humpback Whales which Pass the New Zealand Coast †
Department of Zoology, Victoria University College, Wellington. *
[Received by the Editor, September 5, 1955.]
Route Followed in New Zealand Waters
Factors affecting coastal migration route.
Direction of coastline
Depth of water
Presence of whale feed
Migration in Oceanic Waters
The migration route of humpback whales in New Zealand waters as indicated by approximately 9,000 sightings is described. North-bound humpbacks pass mainly along the eastern coastlines of New Zealand, plus one group passing through Cook Strait to the western side of the North Island and another passing the western side of Stewart Island and round the south-west corner of the South Island before leaving the coast. South-bound humpbacks pass mainly along the western coast of New Zealand, forming a large aggregation near the south-west corner of the South Island, while others follow the east coast of the North Island as far as East Cape, but few occur elsewhere along the eastern coastlines or pass through Cook Strait. Seasonal variation in commencing dates, duration of migration, tune of peak and the periods taken by equivalent proportions of the humpback groups are described for 36 seasons in Cook Strait, three at Whangamumu and four at Centre Island. The rate of migration, times of arrival, peak concentration and latitudinal spread of the migrating stock, at phases of the passage from Antarctic to tropical waters and return, are calculated and discussed.
[Footnote] † This study has been assisted by a grant-in-aid of research from the Research Grants Committee of the University of New Zealand, and the publication of this paper has been financed by the New Zealand Marine Department.
[Footnote] * Now Department of Zoology, University of Sydney.
Of a number of environmental factors discussed as possible modifiers of the route followed by humpbacks in New Zealand coastal waters, the most important appears to be the orientation of coastline in relation to the migration route, which shows some evidence of trends towards the north-west and south-east during the northward and southward migration past New Zealand. While small and localised effects are produced by turbidity, tidal streams, and the presence of whalefeed, no consistent modification of the migration route in relation to bottom topography, direction of ocean currents or the hydrological conditions of differing water masses could be demonstrated. The routes followed by migrating humpbacks in all oceanic waters are consistent with the hypothesis that the main requirement of this species is to reach some area of coastal waters in sub-tropical or tropical regions for normal breeding behaviour, whether near continental shores or small islands. Because of the geographical position of continental land masses and islands in relation to all the oceanic areas, the fulfilling of the above requirement should result in migration routes and segregated populations distributed in almost exactly the oceanic areas in which humpbacks are known to occur.
The migration of whales in general has been a subject of interest to whalers for many centuries and it has long been known that different species follow different seasonal routes, but it was not until Wilkes (1845) and the writings and charts of Maury (1851–55) that the subject received much detailed study. Their work was based more particularly on records from the American sperm and right whalers, but the opening up of new areas and the change in species hunted that followed the introduction of the explosive harpoon by the Norwegians permitted many observations on other species. Collett (1912) when discussing North Atlantic whale catches, mentioned the seasons for humpbacks, but Risting (1912) provided considerably more detail on their coastal movements in this area and also in the South Atlantic, together with mention of Australian seas. His general conclusions on the breeding migrations towards tropical waters and feeding migrations towards polar seas have been reaffirmed for African waters by Olsen (1915) and for the Pacific Ocean by Lillie (1915), while Hinton (1925) provided more South Atlantic data. The review of the migrations of whalebone whales by Kellogg (1928) integrated the preceding and many others on more localised movements, such as described by True (1904) and Alen (1916). Harmer (1931) while primarily discussing blue and fin whales, makes a number of pertinent comments on humpbacks and whale migrations in the southern hemisphere. The charts of Townsend (1935) provide invaluable data on the monthly distribution of whales caught from nineteenth century American whaleships and have been discussed by Matthews (1937) in relation to other observations. The whale marking programme described by Rayner (1940) gave the first definite confirmation of the movements of humpbacks from segregated groups in Antarctic waters to the known breeding areas in tropical waters. Whale mark returns, catch statistics and whale sightings are compared by Mackintosh (1942) who shows that there is strong evidence for believing that humpbacks segregate into five more or less separate groups in Antarctic waters. One of these, the Ross Sea group in Area V, almost certainly represents the summer concentration of humpbacks which pass the coasts of New Zealand, East Australia and other parts of the Pacific as summarised by Dawbin and Falla (1949). It seems probable from the distribution of humpbacks in Area V as indicated by Japanese catches (Omura 1953) that the main summer concentration occurs in the vicinity of the Balleny Islands, and it is presumed that this is the starting point for the northward migration of the humpbacks which pass the New Zealand coast.
Along the New Zealand coasts the humpback is the only whale seen regularly in any considerable numbers. The strongly migratory and coast frequenting habits of this species are known from observations in a number of areas, but few of these areas provide as many alternative routes which can be followed or avoided according to local conditions as are available along the New Zealand coastline. New Zealand is one of the few land masses which is of such a shape and size that humpbacks.
from presumably the same stock can travel along either its eastern or western coasts or even start along one coast and then, because of the position of Cook Strait, can continue along the opposite coast. On their return passage they can follow the same routes in reverse or by slight deviations can follow quite a different coastline in a way which is not possible with a continuous continental shore. As their route is probably not limited so strictly by the position of the coastlines as it is in most areas, the effects of local factors on the whales' migration should be more marked than in other areas. On the other hand the 1,000 mile north-south length of the New Zeaand coastline represents only a small proportion of the total north-south distance traversed by humpbacks each season. However, it is the most southern land mass from which regular observations of Area V whales have been possible, and its present whaling station at Tory Channel (41° S.) is the world's most southerly site for winter whaling.
The history of whale catches and evidence from recent sightings indicate that whales are not as abundant in these waters as in those of the major land masses in the southern hemisphere, but the humpback sightings from parts of the New Zealand coast show that the numbers of this species are by no means insignificant. Whaling in New Zealand waters commenced with the arrival of the “William and Anne” in 1792, but sperm whales were then the main objective and remained so until right whaling commenced in the 1820's. The first two shore stations commenced operations between 1827 and 1829, and were followed by the establishment of many more before 1840, while whaling from overseas vessels in offshore waters increased steadily in the same period, and the numbers of right whales taken reached several hundred per season in the 1830's. It is difficult to fix the date of the first humpback captures in New Zealand waters as some were taken by American whaleships offshore (Townsend 1935) and others by shore parties who rarely kept records, and those who did often listed oil yields only, without specifying the kind of whale caught.
Humpback oil is listed in an account of progress at Cloudy Bay in 1841 (New Zealand Gazette, June 5, 1841), while the letters of John Wade (1842–46) show that humpbacks were being taken in 1843 from at least two of the four stations controlled by him. One of these, “Wydrop”, was in Palliser Bay and the other was at Kaikoura, where 10 humpbacks and two right whales are mentioned as the catch at June 15, 1843. Humpbacks have probably been taken in small numbers from one or other part of the New Zealand coast more or less continuously from at least 1841 until the present day.
By 1900 shore whalers depended primarily on humpbacks, which were taken in five main areas. These were Whangamumu, near the Bay of Islands, Bay of Plenty, Mahia Peninsula, Tory Channel and Kaikoura, and all at that time were operated by the old time methods of open boats and hand harpoons. The explosive harpoon and a steam driven chaser were first used in New Zealand waters by the Whangamumu party in 1910. Launch chasers, as described by Ommaney (1933) were first used with non-explosive harpoons and hand bombs in Cook Strait during 1911, and a light explosive harpoon as well as the hand bombs was first used in 1924. The Kaikoura station operated with launches from 1917 to 1922, but the Mahia stations, which finished operations in 1922, and those in Bay of Plenty operating until 1933, continued with open boats and hand harpoons. The Whangamumu station ceased effective whaling in 1931, so the Tory Channel station is the only one operating at the present time.
Data from various sources listed below provide information on approximately 9000 humpbacks and have been used to deduce the northwards and southwards migration routes of humpbacks in New Zealand waters. The only data suitable for comparing different seasons are those from Tory Channel and Whangamumu whaling stations, and Centre Island lighthouse, which provide some basis for noting
seasonal differences at three points on the New Zealand coast. Data on the sex and age group composition of the humpback stocks passing New Zealand and the results of biological examination of humpbacks caught in Cook Strait during recent seasons will be discussed in succeeding papers.
The material for the present study includes records of approximately 9,000 humpbacks in New Zealand coastal waters recorded as follows:—By whalers at Tory Channel and ex-whalers at other parts of the New Zealand coast; keepers at all manned lighthouses; crews of trawlers and other coastal vessels; various aircraft pilots; logbooks, diaries and other records concerning past whaling station sites. Day by day sightings or catch returns by the Tory Channel whalers have been recorded for 36 seasons and include 4,112 humpbacks, while data from another six seasons brings the total to 5,002 observed or taken in the Cook Strait area. Comparable data for only three of the winter and two of the “summer” seasons are available from Whangamumu for 423 humpbacks, while seasonal tallies for another 18 years total 886, and from Kaikoura for seven seasons total 68. Ex-whalers from sites such as Kaikoura and a number of localities around Mahia Peninsula and Bay of Plenty could not provide dated records, but by interviewing several independently in each area it was possible to obtain corroborated statements on the relative abundance of humpbacks in various months at each locality.
Whale observing from lighthouses was arranged through the courtesy of the New Zealand Marine Department, which asked all keepers to watch for whales, and monthly returns were forwarded by the principal keepers of each of the 29 manned lighthouses around the New Zealand coast (for positions see Fig. 2). During three and a-half years, 1,051 monthly returns were collected, representing some scanning by at least one and usually more men for 30 day periods in each return, but for various reasons, including the unfavourable situation of a number of lighthouses as lookouts for scanning open water, only 118 returns listed definite whale sightings. However, the latter listed approximately 2,000 dated sightings; the exact number being indeterminate because large schools were sighted at some stations and the number of whales in each could be estimated only approximately. In addition, the writer has corresponded directly with a number of the keepers and interviewed others on specific points concerning whale sightings.
An extremely useful supplement to this data was obtained through correspondence, and a number of interviews with the masters of 24 trawlers and some other vessels whose combined operations covered most of the waters inside 10–15 miles of the New Zealand coast. This was especially useful for areas where the lighthouses are unfavourably placed for viewing the open sea or where the whales tend to move too far from the coast to be seen by observers from shore. Aircraft sightings have been forwarded by courtesy of the Royal New Zealand Air Force and the Ministry of Works Aerodromes Branch.
It is necessary to stress that although the actual number of humpbacks sighted at any one time from lighthouses, vessels or aircraft, was usually small, the fact that any were sighted at a particular time by observers who were not trained in whale recognition and who were usually engaged at the time on their own duties, can reasonably be taken as a certain indication that many more humpbacks were in the area than the recorded totals alone would suggest. Only the actual numbers recorded are included in this account, but the circumstances under which the observations were carried out should be borne in mind and due allowance made; especially when comparing such totals with those recorded by professional whalers who maintain a permanent lookout during the whaling season.
There is little specific data on catches from many of the nineteenth century shore station sites, but although right whales were the main objective at first, humpbacks were also taken in increasing numbers, so the location of the station sites is
another useful guide to the coastal pathway of humpbacks. The location of most stations has been previously recorded in the following districts: Southern half of the South Island (Shortland 1851, Hall-Jones 1945); Banks Peninsula (Akaroa Mail Co. 1940); Marlborough (Buick 1900, Macdonald 1933, McIntosh 1940); Hawkes Bay (Wilson 1939); East Coast of North Island (Lambert 1925, Mackay 1949), while other works briefly mention a few more, some of which the writer has been unable to confirm. However, of the 113 station sites shown on Fig. 1 as used at one time or another, many do not appear to have been recorded previously. These were located as a result of interviews with ex-whalers or their descendants, and 103 of the sites have been seen by the writer.
Route followed in New Zealand waters.
The tendency for humpbacks to travel relatively close to land makes them particularly favourable subjects for observations from inshore craft and coastal sites, but it is quite evident from the records to hand that humpbacks do not occur uniformly along the New Zealand coasts. While sporadic sightings of lone humpbacks have been made from almost all sections of the coast, regular seasonal concentrations occur along only certain sections. Before discussing possible reasons for their uneven distribution in New Zealand waters, the observations will be discussed in the following order: North-bound whales travelling up the east coast of both islands; north-bound whales travelling up the west coast of the South Island; northbound whales passing through Cook Strait to continue along the west coast of the North Island; south-bound whales travelling along the east coast of both islands, south-bound whales travelling along the west coast of both islands.
North-bound whales (see Fig. 1) first pass close to or on a path at some distance from and parallel to Stewart Island, but the only definite records from the east coast are those plotted in Chart D by Townsend (1935) These show that nineteenth century American whaleships took some humpbacks at varying distances from shore between May and August only. During these months all would probably be north bound humpbacks. Whaleships were operating in the area at other months of the year as shown by the numerous catches of right whales and sperm whales during November to March, but humpbacks are not plotted for the latter period. There are no lighthouses in this area and very few fishing vessels operate near this uninhabited coast. The only contemporary data is that from one fishing vessel operated by Mr. W. Wellington, who has noted numerous humpbacks during his work around a large portion of the New Zealand coast, but during several seasons off the east coast of Stewart Island between Port Pegasus and Half Moon Bay he saw very few humpbacks even during months when the whales were abundant near Centre Island on the north-western side of Stewart Island.
Immediately to the north a long series of observations were made by the lighthouse keepers at Dog Island (five miles south-east of Bluff) and from Waipapa Point (see Fig. 2), on the South Island 25 miles east of Bluff. Each provided 43 monthly returns, but during the three and a-half years only one humpback was sighted and this was seen from Dog Island in May. From Nugget Point lighthouse (halfway between Bluff and Otago Peninsula) there was one sighting of a north-bound humpback in May and two in June, while at Cape Saunders on Otago Peninsula there was one sighting in May, five in June, eight in July, and one in August during the same period, but in 1954 up to 20 or more per day were seen during June. Between the neighbourhood of Bluff and Otago Peninsula there were nineteenth century whaling sites situated, according to Shortland (1851) and Hall-Jones (1945), at a number of the suitably sheltered coves including at least the following: Aparima (Riverton), Oue, Omaui (New River), Awarua (Bluff), Toitois (Fortrose), Waikawa, Tautuku Bay, Matau (Molyneux), Taieri. (See Fig. 1, Nos. 2–10.)
Fig. 1—The route taken by north-bound humpbacks in New Zealand coastal waters indicated by solid lines. Stipple indicates the main areas where humpbacks are inferred to approach or leave the coastal waters. Localities which have been used as whaling station sites are shown as follows:—1, Rakituma (Preservation Inlet). 2, Aparima (Riverton). 3, Oue (Sandy Point). 4, Omaui (New River). 5, Awarua (Bluff). 6, Toitois (Fortrose). 7, Waikawa. 8, Tautuku Bay. 9, Matau (Molyneux). 10, Taieri. 11, Taiaroa (Otago Harbour). 12, Purakanui. 13, Wakiouaiti (Karitane). 14, Onekaraka (Moeraki). 15, Patiti Point. 16, Caroline Bay (Timaru). 17–19, Banks Peninsula. Goashore (Ohahoa); Ikarangi; Peraki; Island Bay. 20, Port Cooper (Lyttelton Harbour). 21, Motunou Island. 22, Goose Bay. 23, Kaikoura. 24–31, Port Underwood: Kakapo; Ocean Bay (2); Tom Kanes Bay (2); Pipi Bay; Whangatoetoe Bay; Cutters Bay. 32–36, Tory Channel: Te Awaiti (several); Jacksons; Bay; Yellerton; Fishing Bay. 37, Wyderop (Palliser Bay). 38, Tuingara (Pourere). 39, Waimarama. 40, Putotaranui. 41, Rangaika. 42, Te Awanga. 43, Clifton. 44, Whakaari (Tangoio Bluff). 45, Moeangiangi. 46, Mohaka. 47, Whakamahia. 48, Wairoa. 49, Waikokopu. 50, Mahia. 51–56, Western side Mahia Peninsula: Kinikini (Long Point); Moimotu; Te Hoe; Te Kereru. Tauranganui. Portland Island 57–60, Poverty Bay: Turanganui; Waikahua, Papawharaiki; Tuahine Pt. 61, Whangara. 62, Pokatakino (near Gable End Foreland). 63, Tolaga Bay. 64, Anaura Bay. 65, Te Mawhai. 66, Tokomaru Bay. 67, Waipiro Bay. 68, Tuparoa. 69, Port Awanui. 70–72, Near Te Araroa: Te Hekawa, Wharariki, Waipao. 73, Matakaoa Pt. 74, Whaiti (near Cape Runaway). 75, Whangaparaoa. 76, Waihau Bay. 77, Pahou. 78, Maungaroa. 79, Te Kaha. 80, Awanui Bay. 81, Omaio. 82, Whitianga. 83, Maraenui. 84, Torere. 85, Whale Island. 86, Mercury Bay. 87, Whangaruru. 88, Whangamumu. 89–90, Bay of Islands: Ninepins Island, Moturoa Island. 91, Matauri Bay. 92, Cavalli Islands. 93, Wainui Bay 94, Stephensons Island 95, Seasick Bay (Whangaroa Harbour). 96, Taupo Bay. 97, Waimahana Bay. 98, Taemaro Bay. 99, Moturoa Island (off Cape Karikari). 100, Houhora 101, Parengarenga Harbour. 102, North Cape 103, Coalheaver (Te Korohiwa) 104, Mana. 105, Porirua. 106–111, Kapiti Island: Rangatira; Te Kahua; Waiorua Bay; Hikos Island (Motungarara); Ruaparahas Island (Taharamaurea); Evans Island (Tokamapuna). 112, Wanganui. 113, Moturoa (New Plymouth).
These stations were established prior to 1840 and worked for an average of three seasons each, ranging from one to six. Catches in the opening season, as calculated from oil yields, ranged from about 10 to 25 whales per station, but diminished at each until the stations closed down in turn, and the total number of whales taken from all these stations was probably less than 300. As there is no mention of humpbacks in this catch it is presumed that all were right whales which evidently came closer inshore than do humpbacks. Even in the 15 to 20 miles offshore belt covered by trawlers, humpback sightings have been relatively few up to Otago Peninsula (Captain J. Black) except for the 1954 season. Between Otago and Banks Peninsula the only manned lighthouse is at Moeraki, but no humpbacks were seen inshore at this point during three and a-half years. Mr. F. Abernethy, who was on coastal vessels for seven years travelling south past Akaroa in a direct line for Otago Peninsula and then returning north inshore along the coast to Oamaru and Timaru stated that humpbacks were frequently sighted on the direct route—i e., travelling outside Canterbury Bight, but they were very seldom seen inshore along the coast of Canterbury Bight. In the nineteenth century the whaling station sites along this coast south of Akaroa were located at Taiaroa (this was in Otago Harbour, but there is some evidence that at least two, and probably three, “fisheries” operated in this harbour), Purakanui, Waikouaiti (now Karitane) and Onekaraka (near Moeraki) according to Shortland (1851), and at Patiti Point, Caroline Bay (Timaru), Goashore (Ohahoa), Ikarangi, Peraki and Island Bay with the four latter all situated on the south coast of Banks Peninsula. (See Fig. 1, Nos. 11–19.) Like the whalers further south, those from the above stations were catching chiefly right whales, which came closer inshore here also than do the humpbacks to-day. From the Taiaroa station about 300 right whales were taken in nine years, but at least 100 more were taken in the same area by visiting whaleships, while more than 300 (calculated from data in Shortland, 1851) were taken in a six-year period from Waikouaiti and Onekaraka, which are both situated west of the route followed by the humpbacks. From Peraki, humpbacks were occasionally seen as they were mentioned in Hemplemann's log
(Anson 1910), but apparently were not hunted at the time of this station's full scale operations 1837–1843.
There are two manned lighthouses on Banks Peninsula, one on its outer coast (Akaroa) and the other well inside Pegasus Bay at the entrance to Lyttelton Harbour (Godley Head). From the former one north-bound humpback was noted in May, twelve in June, and 37 in July, while none were seen from Godly Head. In the coastal waters up to 10 miles offshore from Banks Peninsula a number of fishing vessels operate, and from one of these Mr. L. M. Chapman has reported some of his own and his colleagues' observations. These include regular sightings of one to three per day of north-bound humpbacks along the outer coast during June and July with small numbers in August, and the latest sighting reported was August 12. Humpbacks were observed between 100 yards off the coast up to 10 miles east, which was as far out as the vessels travelled.
Between Banks Peninsula and Kaikoura there are no manned lighthouses, and there have been no records of close inshore whale sightings by coastal vessels. Mr. F. Abernethy states that on the course from Wellington or past Cape Campbell to Lyttelton, whales are rarely seen inshore to Pegasus Bay but further offshore in a line passing to the east of Banks Peninsula, humpbanks are encountered between May and August. There were former whaling stations for possibly only a season or so at Port Cooper (Lyttelton Harbout) and another for several seasons in the mid-1840's at Motunou Island in Pegasus Bay, but both were catching right whales.
In the Kaikoura region (Fig. 1, 22 and 23) whaling commenced in 1843 at Waiopuka on the Kaikoura Peninsula, and humpbacks formed the greater part of the catch in that year at least (Wade 1842–6). In the following year shore stations were started at South Bay (also on the Peninsula), at Waipapa to the north and at Amui to the South, while a site at O te Rangi Uni Wai (between Amuri and Kaikoura) was used later for a number of years (Watts 1930). No indication of the species caught from the latter sites has yet been obtained. At Kaikoura Peninsula and Goose Bay, 12 miles south-west, whaling was carried on into the 20th century. Ex-whalers state that humpbacks were the main catch at least between 1890 and the closing of the Kaikoura station in 1922. The only records of actual catches taken are for the years 1917–1922, when light launches harpooned 74 whales, of which 68 were humpbacks, five were right whales and one a sperm whale. Many more humpbacks were, and still are, sighted in the area, and the station was abandoned only because of lack of shelter for light chasers.
Fishermen working off Kaikoura in 1954 sighted up to 30 humpbacks per day at the time when sightings of this order were being made from the Tory Channel lookout. From Kaikoura for some distance northwards towards Cape Campbell there are frequent reports from observers on coastal shipping, fishing vessels and aircraft, and nearly all the reports are of whales within a mile or so of the general trend of the coast. Near Cape Campbell, all the evidence available indicates that humpbacks move further out from the coast. The sightings from the Cape Campbell lighthouse during four years were negligible, and fishermen who trawl regularly nearby do not see humpbacks even on days when 20 or more are being sighted further north in Cook Strait. From the lookout at the entrance of Tory Channel the great majority of humpbacks are seen coming to Cook Strait from the south-east, and it is so exceptional to see one approaching along the coast from Cape Campbell and past Cloudy Bay that there can be no doubt that the stock which move up past Kaikoura detour away from the coast before entering Cook Strait. In this area, the total number of humpbacks recorded by the Tory Channel whalers during 36 seasons has been approximately 5,000.
In addition, a few right whales are still seen occasionally from the lookout, and it has been noted that these follow the coastline much more closely than do humpbacks, and they usually approach Cook Strait from along the coast of Cloudy Bay.
In the 1830's and 1840's intensive right whaling was carried on from vessels anchored in Cloudy Bay. At the same time other vessels operated in and about Port Underwood nearby, and the small bays within had up to eight shore parties engaged in catching right whales, while other parties from Tory Channel took part in the same coastal sector (see Fig. 1, Nos. 24–36). Whaling from Tory Channel has persisted until the present day, but before the end of the nineteenth century the decline in right whales had led to a change over to humpbacks.
The data from the east coast of the South Island indicates that humpbacks travel in a relatively straight line between headlands and only occasionally come close inshore into the bays and bights (Fig. 1). Very helpful co-operation from the Royal New Zealand Air Force provided some opportunities to investigate this question by taking the writer and another observer (B. M. Bary) on flights from Wigram Aerodrome (Christchurch) to Kaikoura in the north and Timaru in the south. For four days in mid-July, 1949, the navigational flights were arranged to traverse waters 20 to 50 miles from the coast, flying between 800 to 1,000 feet altitude at a speed of approximately 110 m.p.h. Under the dull lighting conditions of those days, it was not possible to see whales except at the surface, which reduced possible sightings to those of whales actually spouting at the time the plane was passing overhead. On July 17, two humpbacks were seen about 60 miles north-east of Banks Peninsula—i.e., about 50 miles east of the nearest coast. On July 18 two were seen 25 miles north-east of Banks Peninsula, so these two sets of observations showed that some whales, at least, were travelling north further offshore instead of turning west past Banks Peninsula to follow the coastline closely. No whales were observed during our flights offshore between Banks Peninsula and Timaru, but two interesting sightings in this area were reported by the R.N.Z.A.F. pilots in April, 1950. The first was on April 11, which was the earliest date recorded for a whale in that year and was over a month earlier than the first capture of a whale near Tory Channel, in 1950. The whale was sighted at 44° 50′ S./171° 40′ E., and was heading northwards, while on April 13 “2 or 3” were observed “4 miles S.E. of the Rakaia River mouth” and were also heading northwards. A school of approximately 20 was sighted further east on the same day, but these were probably sperm whales. Both the probable humpback records were inside the Canterbury Bight, and the second sighting was relatively close to shore in a position from which the whale would have to travel about 50 miles to the east in order to pass Banks Peninsula. These whales, at least, had tended to come in towards the coast even at a point which would necessitate a deviation to the east before the course northwards could be resumed further on.
The most striking feature of the humpback movement along the east coast of the South Island is the apparent increase in the number of whales sighted from Port Pegasus, Stewart Island, up to Cook Strait. As the west to east slope of this coast extends through nearly seven degrees of longitude, this increase could well be due to north-bound whales striking at various points up the coast and then being necessarily deflected along it where they join other whales which had originally been travelling some distance further east. On reaching Cook Strait the majority pass through to travel off the west coast of the North Island, but the further course of these whales will be discussed later.
Along the southern coast of the North Island few humpbacks are seen close inshore, and in the 36 and 43 monthly returns from the Pencarrow and Baring Head lighthouses respectively only one humpback (in July) was reported. Further offshore in this area they are seen, and the master of the inter-island ferry “Rangitira” has reported numerous sightings about six miles to the south-west of Baring Head—i.e., on the eastern approaches to Cook Strait, while several Wellington fishermen have reported a number of sightings to the south of Karori Rocks, which are still closer to the Strait. These whales were probably deflected to the west by the coastline and would also tend to pass through Cook Strait, where the local whalers sometimes see considerable numbers moving along the eastern side of the Strait.
From between Baring Head and Cape Palliser there is as yet no evidence as to whether humpbacks go west through Cook Strait or turn east to travel up the east coast of the North Island, and although some humpbacks were taken from a station in Palliser Bay in 1843 (Wade 1842–1846) there is no indication of their direction of travel. The sightings of north-bound humpbacks from Cape Palliser lighthouse are as follows:—June (6), July (2), August (1), while three Wellington trawlers which operate along this coast as far north as Castlepoint have reported seeing humpbacks regularly from one to five miles offshore, between May and August, but there were only two June sightings reported from Castlepoint lighthouse.
There are no manned lighthouses between Castlepoint and Portland Island; at the northern end of Hawke Bay, but several trawler masters have provided some data on this portion of the coast, and some whaling was carried on from Mahia Peninsula until 1922, so a number of ex-whalers in the area were interviewed. Between a point some miles to the south of Cape Kidnappers and Mahia Peninsula, Mr. J. O. Tait and Mr. H. W. Forrest have reported humpbacks moving north singly or in pairs during the winter months (May to August). South of Cape Kidnappers the whales generally keep between five and ten miles offshore, and they do not usually follow the coast into Hawke Bay but many do strike the coast at its northernmost portion immediately west of Mahia Peninsula. From Portland Island, which is at the southern end of the Peninsula, almost all the sightings by lighthouse keepers were of whales from half a mile to two miles west of the island. Those specifically reported were as follows: May (2), June (14), and July (7), but coastal craft and ex-whalers state that there were “many more”. Whales travelling to the west of Portland Island meet a cul-de-sac made by a low-lying sandspit joining Mahia Peninsula to the North Island, and it is probable that until relatively recent times whales could have passed through a channel separating the two pieces of land, but they now have to turn back about 20 miles due south before they can round the peninsula and continue north. Most of the whales taken were caught at the head of the bay between Waikokopu and Mahia, and numerous small shore stations were situated in bays along the west coast of the peninsula. The whaling sites in addition to Waikokopu and Mahia included the following on Mahia Peninsula: Kinikini, Moimotu, Te Hoe, Te Kereru, Tauranganui and Portland Island (see Fig. 2, Nos. 49–56), and there is considerable doubt as to whether any were situated along the eastern coast of the peninsula. While right whales were taken in the mid-nineteenth century, Mr. Ra. Bartlett, one of the surviving whalers, informed me that humpbacks were the main catch in the late 19th century and up to the cessation of whaling in 1922. According to Mr. Bartlett, whaling was carried on from May to September, and he says that humpbacks can still be seen there at this time of year.
Inside and to the south of Hawke Bay there were nineteenth century whaling sites situated from south to north at the following: Tuingara (Pourere), Waimarama, Putotaranui, Rangaika (all south of Cape Kidnappers), Te Awanga, Clifton, Whakaari (near Tangoio Bluff), Moeangiangi, Mohaka, Whakamahia and Wairoa (all inside Hawke Bay), (see Fig. 1, Nos. 38–48). From the latter, right whales were the main catch, and this once again illustrates the manner in which this species penetrated close to shore along coastal indentations which tend to be by-passed by humpbacks.
Between Mahia Peninsula and Hicks Bay, the only manned lighthouse is at East Cape, but it does not face the open sea and is not satisfactory for whale observation. Mr. J. Bonica, who operates a trawler from Gisborne, has reported north-bound humpbacks along this whole coast in May and June. A number of observers have confirmed this and added sightings of humpbacks in July and August. Several exwhalers interviewed along this coast stated that humpbacks were taken as well as right whales from some, at least, of the abundant shore stations in this area during
the nineteenth century. Sites so far located from south to north are as follows: Turanganui, Waikahua, Papawharaiki, Tuahine Point (all Poverty Bay), Whangara, Pokatakino (south of Gable End Foreland), Tolaga Bay, Anaura, Te Mawhai, Tokomaru Bay, Waipiro Bay, Tuparoa, Port Awanui, Te Hekawa, Wharariki, Waipao (last three east of Te Araroa) and Matakaoa Point. (See Fig. 1, Nos. 57–73).
Once past East Cape and Hicks Bay, north-bound humpbacks which travelled due north would be at an increasing distance from land where sightings would be few, but a number must turn well to the west travelling offshore in the general trend of the coast as they have been seen from Cuvier Island lighthouse to the west of Bay of Plenty in May. A few only travel south-west for a sufficient distance to reach the head of the Bay of Plenty, and the numerous shore whaling stations in this area captured chiefly south-bound humpbacks later in the season.
According to Mr. Gilliver, who, when Inspector of Fisheries at Tauranga, patrolled the Bay of Plenty frequently, there is a regular stream of humpbacks which come round East Cape and pass inside White Island but outside Whale Island, and are therefore about five or more miles from the coast in water of 20 to 25. fathoms They pass close to the northern coast of Motiti Island and then on past Mayor Island and the Alderman Islands towards Cuvier Island and the Colville Channel. A similar course has been described independently by Messrs. Charles Mark, George Mark and W. Sampson, the masters of three trawlers which work in the area, and they all agree that humpbacks singly, in pairs or in a group of up to five per day are seen along this narrow strip of water but seldom any closer inshore and less frequently at greater distances outside than in the above route. For some years late in the nineteenth century, whaling occurred from sites near Mercury Bay, a little south of the Colville Channel. Mr. W. Wellington, who was fishing for several years north of Hauraki Gulf, states that he has observed humpbacks beyond the Colville Channel in June passing between the Barrier Islands travelling north-west towards Whangaruru and Cape Brett.
At Whangaruru whaling was carried on for a few seasons commencing in 1890 as well as at Whangamumu, about 15 miles further north. From the latter whaling continued until 1931, resulting in the catches as shown in Table I. The dates for whale sightings show that north-bound humpbacks pass these harbours mainly in June, July and August.
Former Whangamumu whalers informed me that whales approached from a south-easterly direction and usually neared the coast at or a little to the south of the station and then followed the coastline very closely. Advantage of this was taken in the period during which net whaling was carried out (1893–1910), by lashing together six wire nets, each 60 feet long, to extend across the channel between shore and a rock about 100 yards away. While the catch by this method seldom exceeded a dozen whales per season, it is of interest that nearly all the whales caught, according to a local whaler, were entangled in the net nearest shore and had thus funnelled into a channel of only 60 feet width. A log of the 1898 net whaling season was kept by the late Mr. George Cook, and his son, Mr. G. Cook, of Auckland, has kindly allowed me to examine it. It records sightings as well as captures, commencing on June 10 and ending on August 4, and during this period 117 humpbacks were seen from the coast. Of this number, 10 were travelling sufficiently near shore to foul the nets or be caught in them. From Net Rock and immediately beyond it the northward moving humpbacks veered out to Cape Brett, and while most travelled further offshore up the remaining portion of the North Island coast, humpbacks were taken from this coast until about 1904. There were stations operating with open boats from Matauri Bay and Cavalli Islands, Wainui Bay, Seasick Bay in Whangaroa Harbour and Stephensons Island at the entrance, Taupo, Waimahana and Taemaro Bays, Moturoa Island, Houhora, Parengarenga Harbour (in the 1850's), and at North Cape. (See Fig. 1, Nos. 91–102.) Fishermen and coastal vessels still frequently sight humpbacks along this coast.
Offshore to the north-east of North Cape, Townsend (1935) shows a concentration of humpback catches made during July, August and September by American whalemen. The catches in this area presumably represent those from the last northbound humpbacks to pass along the east coast of the North Island, but it is possible that humpbacks seen from Cape Reinga lighthouse in July had come west from North Cape.
During the months in which some north-bound humpbacks are following the course described above, others pass along parts of the west coast of the South Island and may possibly be joined by those which pass through Cook Strait to travel offshore to the west of the North Island (Fig. 1). The furthest south New Zealand locality from which data have been provided is Centre Island, situated near Riverton on a line running due north from the west coast of Stewart Island. There are no data available from this uninhabited coast of Stewart Island, but the fact that there have been numerous humpback sitings from Centre Island lighthouse and only one from Dog Island and other parts of Foveaux Strait at the same time of year strongly indicates that the whales near Centre Island must have approached from along the western coast of Stewart Island. Sightings recorded were as follows: May (70), June (104), July (38), August (6). These whales have to travel almost due west for about 60 miles before rounding Puysegur Point to continue northwards. From the lighthouse there, north-bound whales have been recorded in May (unspecified number), June (23), July (16), August (4), but it is clear from from returns from fishermen passing the area that many more humpbacks migrate past a few miles offshore beyond the range of visibility of the lighthouse keepers. Some of the whales even enter the southern fiords and travel well up Preservation Inlet and Dusky Sound before returning to continue north.
A shore station was started in Preservation Inlet (see Fig. 1, No. 1) in 1829 and for the years 1835 and 1836, 46 and 45 whales were taken respectively (Shortland 1851). Oil returns for the earlier seasons indicate that catches for these seasons were slightly less, but although the species are not named, descriptions of “treating whalebone” show that right whales were the main objective.
Large numbers of humpbacks were noted two miles outside Dusky Sound in mid-June, 1953, by Mr. J. Warcup, of Dunedin, and a number of observers from fishing vessels have noted humpbacks past Milford Sound and as far north as Jacksons Bay. Captain P. E. Charles has reported humpbacks in groups of up to a dozen at a time moving past Cascades and into Jacksons Bay, where he has observed them waving flippers out of the water and cruising about slowly for days on end. While he states that this has been noted regularly during his eight years travelling past this coast, he reports that humpbacks are very seldom seen north of Jacksons Bay.
I have obtained little positive data from along the remaining portion of the west coast. All 35 monthly returns from Kahurangi Point lighthouse near the northern end of this coast were negative, but the lighthouse is manned only part-time. The only other lighthouse is on Farewell Spit, but the lighthouse is situated at the end of an easterly directed sand spit which brings it far away from the probable course of any humpbacks which might pass along the northern portion of the west coast and all 43 monthly returns reported “no sightings”.
There have been no shore whaling stations established on this coast north of Preservation Inlet and the catches from American whaleships plotted by Townsend (1935) show no humpbacks taken along this coast, although a few right whales were taken as far north as Greymouth, including some in May. These captures, together with some sperm whales taken offshore as far north as Westport during April and May, show that some whaleships were operating in the area at a time when north-bound humpbacks could be expected.
The masters and crew of three vessels which traversed these waters regularly (Hauiti, Kokiri, Karamu) have all agreed on the rarity of whale sightings along
this coast, and in a twelve-month period have reported only four humpbacks, of which two were probably south-bound. It therefore appears to be reasonably certain that the main group of humpbacks seen so frequently further south must leave the coast at a point somewhere near Jacksons Bay and then continue to the north or north-west in a line which takes them outside the waters traversed by coastal shipping.
Along the west coast of the North Island (Fig. 1) sightings are almost certainly those of whales which came north through Cook Strait as described earlier. The migration through these waters is the most widely known feature of whale movements near New Zealand, and it has been known to whalers for nearly a century and a-half. The earliest catches in the vicinity were taken from whaling vessels, and the first shore station, established in Tory Channel in 1827, was the forerunner of a large number on either side of Cook Strait between 1830 and 1850.
In Port Underwood (formerly termed Cloudy Bay) at least eight shore stations operated, while many whale ships worked in the area at the same time. Approximately five sites were used inside the entrance to Tory Channel (see Fig. 1, Nos. 24–36), and on the northern side of the Strait there were stations established at Te Korohiwa (south of Porirua Harbour), inside Porirua Harbour, on Mana Island and each of the three larger islets on the landward side of Kapiti Island, three on the eastern shores of Kapiti Island and one at the mouth of the Wanganui River (see Fig. 1, Nos. 103–112). No early logs specifically mentioning the species taken from the shore stations have been located and although it is clear from the amounts of whalebone exported that right whales were a major part of the catch, it is also clear from Townsend (1935) Chart D that American whaleships in the same waters were frequently taking humpbacks between May and August. Their catches of right whales on either side of Cook Strait also occurred in these months, being greatest in July, but catches continued three months later than for humpbacks. Contemporary data for humpbacks confirm that from the American whaleships, but also show that these whales tend to travel relatively close inshore at the southern portion of the North Island. Sightings from the Brothers lighthouse were: May (1), June (18), July (16), August (2), while from Stephens Island lighthouse, 40 miles to the north-west, there were only two sightings in May and one in August during the same period. Fishermen operating from Porirua Harbour frequently encounter humpbacks near Mana and Kapiti Islands during the above months, but apart from two humpback strandings in August near the mouth of the Manawatu River and two July sightings by Mr. F. Abernethy offshore from Wanganui, there is little specific data on the passage between Kapiti Island and Cape Egmont, and all returns from a lighthouse at the latter were negative. However, the principal keeper at Cape Egmont wrote saying that “owing to the lack of altitude and the general unfavourable outlook seaward, the chances of whales passing being sighted are very small”
North of Cape Egmont the coastline curves east into the North Taranaki Bight and several fishermen from New Plymouth work in this area from shore to 20 miles seaward as far north as Kawhia. Two of these, Mr. R. C. Rutherford and Mr. D. J. Holmes, have reported sightings of south-bound whales, but no definite sightings of north-bound whales from May to August. Only one small shore station was established between Cape Egmont and the most northern portion of the North Island coast. It was situated near the Sugar Loaf Rocks (see Fig. 1, No. 113), New Plymouth, and operated in the 1840's. According to Weeke's Journal of 1841 (Rutherford & Skinner 1940), whales were not seen from this station until the end of June. He describes successful hunting by the whalers in July and August, but does not describe the species caught, and while he refers to the trying out of oil, he makes no mention of collecting whalebone which was quite often the only product saved by right whalers at shore stations.
Fig. 2.—The route taken by south-bound humpbacks in New Zealand coastal waters. Solid lines and stipple as in Fig. 1. The position of lighthouses from which regular whale observations were made are shown as follows: 1, Puysegur Point. 2, Centre Island. 3, Dog Island. 4, Waipapa Point. 5, Nugget Point. 6, Cape Saunders. 7, Moeraki. 8, Akaroa. 9, Godley Head. 10, Cape Campbell. 11, Pencarrow. 12, Baring Head. 13, Cape Pallister. 14, Castlepoint. 15, Portland Island. 16, East Cape. 17, Cuvier Island. 18, Tiritiri. 19, Mokohinau Island. 20, Cape Brett. 21, Cape Reinga. 22, Kahurangi Point. 23, Farewell Spit 24, French Pass. 25, Stephens Island. 26, Brothers Island. 27, Cape Egmont. 28, Manakau. 29, Kaipara.
Between Kawhia and Cape Reinga there are three lighthouses—namely, Manakau, Kaipara and Cape Reinga. The two former reported nil sightings for 13 and 40 months respectively, but both are poorly situated for whale sightings. Manakau is manned only part-time, and at Kaipara the living quarters of the keepers are situated inside the heads. From this coast the master of only one fishing vessel, operating from Kawhia, has reported sighting three humpbacks travelling north in mid-June, and none in other months. The largely negative information from the northern half of the west coast of the North Island suggests that humpbacks passing here behave similarly to those passing the west coast of the South Island—i.e., once they have rounded the most westerly point of land across their course, they cease to follow the coastline closely and continue their migration north at some distance from the coast. A route due north from Cape Egmont would bring them near the west coast again a little south of Cape Reinga, but four sightings in July are all that were reported for north-bound whales during four consecutive seasons' observations from the Cape Reinga lighthouse, and as noted previously, it is possible that these came west from North Cape.
The majority of the humpbacks therefore appear to travel at least a little to the west of a course due north, a trend which is certainly evident with a large number of north-bound humpbacks along the east coast of the North Island. This trend if continued would take both these groups of whales past Norfolk Island and New Caledonia towards the known breeding ground in the Coral Sea.
South-bound Humpbacks. (See Fig. 2.)
The earliest humpbacks regularly sighted are seen from Cape Reinga lighthouse in September. The 14 reported were all noted as travelling east indicating that instead of moving south along the west coast of the North Island, they were moving in the direction of North Cape and would presumably then turn south along the eastern coast of the North Island (Fig. 2). In October and November, two and six respectively were reported moving in the same direction, and it is of interest that there was said to be a nineteenth century shore station situated on this northern coast at Tom Bowling Bay. From North Cape to Bay of Islands humpbacks follow the south-east trend of the coast closely and have been sighted regularly passing the headlands bordering Doubtless Bay, and in a single season eight were sighted inside the Bay itself (Mr. D. J. Mackay). A late concentration has been reported by Mr. C. Mark, of the “Waikawa”, who described a “large” school of humpbacks cruising slowly and lying on their sides waving flippers out of the water five miles from Doubtless Bay in January, 1954. From the shore stations so closely spaced along this coast as described previously, southbound whales were seen in approximately the same numbers as the earlier north-bound humpbacks, but as the former are frequently accompanied by calves the whalers from open boats obtained their catches most readily in September and October by fastening to the calves and then killing the cow. Some humpbacks follow the coast so closely that they pass Ninepins Island on the western side of the Bay of Islands, and whaling was carried out from this site for a number of spring seasons in the early 1890's. The Norwegian whaling expedition of 1912 also operated from this area, using Moturoa Island and Whangaroa Harbour as bases, and by November they had taken 80 humpbacks (Hansard, November 4, 1912). From Cape Brett lighthouse the keepers have reported humpbacks moving south in September (6), October (14), and November (10). A number of ex-whalers from the former Whangamumu station independently told me that humpbacks moving south continued south-east from Cape Brett so that the whalers had to go further out to sea for their catch from this group of whales and net whaling close inshore was not possible. At times insufficient humpbacks were sighted from the coast to keep the small Whangamumu factory working, and the late Mr. H. F. Cook then went about 20 miles offshore and usually found that humpbacks were travelling in much larger numbers at this distance from the coast than
close to shore. Logbook data on some of these “summer seasons” will be described later. The season was somewhat shorter than for north-bound whales, indicating that the whales were travelling in a more compact group, although the sightings were approximately the same as for the May/August season. Usually south-bound whales were observed and hunted for the two months from late September to late November, but in one exceptional season humpbacks were caught until December 11. Cows accompanied by calves were frequently noted amongst the south-bound whales, and occasionally the whales were seen feeding.
The course south of Whangamumu follows parallel to the coast, taking some of the whales into Hauraki Gulf (Fig. 2). Ten humpbacks were sighted off Waipu Cove, just north of Bream Tail by the master of the Navy Department vessel “Endeavour” when operating in the area for a few days during November. Between October and January six were reported by keepers at Mokohinau lighthouse, 35 miles east of Waipu Cove, while two vessels sighted approximately 15 near the Hen and Chicken Islands and two near Little Barrier in early January, 1954.
The masters and crew of five fishing vessels which work from Auckland, and Messrs. Cole and Nolan, of the Kia Ora Fish Mart, all informed me that they frequently sight south-bound humpbacks inside and at the approaches to Hauraki Gulf. Some pass between Little Barrier and Cape Rodney on the mainland, and others between Little and Great Barrier Islands, especially during November. They have been seen as close inshore as the channel between Kawau Island and the mainland in November, and near Tiri Tiri Island, 10 miles to the south. According to the fishermen, the distance which whales extend south into the Gulf and the time they spend in this area varies from year to year, depending on the local blooming of whalefeed. This occurs at any time between September and March, and is usually more abundant in the Bay of Plenty. When whalefeed is plentiful in Hauraki Gulf at this season, many of the whales come well into the Gulf and are seen cruising slowly as though feeding as far south as the Noises, which are a group of small islets about 15 miles offshore from Auckland City. During such seasons I am informed that humpbacks may remain until late January and from a small vessel servicing the Mokohinau lighthouse in mid-January, five humpbacks were sighted as the vessel travelled up Hauraki Gulf. Untortunately no collections of whalefeed have yet been received for identification, but the description given to me strongly suggest that it is Munida sp.
During a survey combined with whale marking carried out by Mr. T. Norton and the writer from Marine Department Fisheries patrol vessels for three weeks in October, 1955, only five humpbacks were encountered in the Hauraki Gulf area. Two schools with 30 to 40 sei whales in each were encountered, one school being near Poor Knights Island and the other near the northern end of Little Barrier Island. Both groups appeared to be feeding and remained almost stationary in their respective areas for more than two weeks before dispersing. The survey and many enquiries during and after the project, failed to reveal the local route followed in 1955 by south-bound humpbacks which earlier passed Cape Brett.
In most seasons, while some humpbacks are entering Hauraki Gulf, others at the same time (October to December) pass outside the Barrier Islands or between Great Barrier and Coromandel Peninsula to enter the Bay of Plenty, and are joined by those from the Hauraki Gulf. En route they are seen passing Cuvier Island (20 in November) and then between the eastern Coromandel coast and Mayor Island to pass north of Karewa (Mr. W. Wellington) and close to the northern side of Motiti Island, where they turn in an easterly direction to travel at about two to five miles offshore until they meet the north-westerly trend of the coast beyond Opotiki to Cape Runaway (Mr. E. W. Gilliver).
A series of small shore whaling stations commenced operations along the eastern Bay of Plenty coast in the 1830's and 1840's and were continued by Maoris using
open boats until 1933 (Dawbin 1954). The stations from west to east were as follows: Whale Island, Torere (10 miles east of Opotiki near the head of Bay of Plenty), Maraenui, Whitianga, Omaio, Awanui Bay, Te Kaha, Maungaroa, Pahou, Waihau Bay, Whangaparaoa, and Whaiti (see Fig. 1, Nos. 85–74). A number of former whalers at these stations have been interviewed, but I am especially indebted to Mr. H. Ngamotu, of Te Kaha, for data on whaling in this area, and the chief points relevant to this paper are that humpbacks have been the main catch since 1900, at least, and it was and still is the only species of whale sighted frequntly. All the catches were south-bound whales taken in the spring months (mainly October and November), and as the catches were made by the old techniques using hand harpoons and rowing boats, they represent only a small proportion of the actual totals sighted. The proximity of adjacent stations produced such competition for the same whales that individual stations averaged only a few whales per season, but the writer has not yet been able to obtain accurate data on the total catch per season for the area as a whole. The total is not likely to exceed 30 humpbacks per season, but it is clear that humpbacks enter the eastern part of the Bay of Plenty in considerable numbers before they pass the obstructing land masses around to East Cape. Their rate of progress through this area is slower than when the whales are north-bound, and this may be due to feeding, as there are usually numerous patches of red “shrimps” sometimes square miles in area in the Bay of Plenty between September and March. The whales are not, however, seen regularly in these waters after the end of November.
They have been observed near Te Araroa in December, but relatively few reports of positive sightings have been obtained from the North Island coast south of East Cape. In contrast to the numerous reports of north-bound whales passing within sight of Portland Island lighthouse, there were only four reports of south-bound whales during three years' observations. All were sighted in late October, and fishermen have not reported any between this locality and East Cape; but two humpbacks offshore from Tolaga Bay were reported from H.M.N.Z.S. “Lachlan” when passing the area in early December. The paucity of reports suggests that after rounding East Cape, the majority of the whales continue due south or south-east, which would take them an increasing distance from land as they moved further south. Some, however, come back to the coastline as Mr. P. A. Munro has reported a number of sightings from his trawler, which works between Mahia Peninsula and Cape Turnagain. He reported humpbacks off the east coast of Mahia Peninsula in December and January, and on a line between the above and Cape Kidnappers—i.e., about 25–30 miles east of Napier. He has observed them in small schools from October onwards along this route, and south of Cape Kidnappers he has observed them in greatest numbers offshore in water of 20 fathoms between Black Head and Cape Turnagain. Along the whole of the route observed by Mr. Munro he has noted that fish were especially abundant in the areas where whales were cruising, and although he has not reported whales feeding, his descriptions strongly suggest that whales and fish were both congregating at patches of feed as described previously for the Bay of Plenty.
No south-bound humpbacks were reported from Castlepoint lighthouse, but the crews of trawlers, especially of the “Maimai” and “Thomas Currel”, when working in the area in October and November, sighted sporadic humpbacks and occasionally a pair travelling south, while from Cape Palliser lighthouse 20 humpbacks were reported between early October and the end of December. From, along the east coast of the South Island all lighthouse returns for October to January were negative except for a single sighting from Cape Saunders in October and two from Nugget Point in November. In contrast to the winter month sightings, fishing and coastal vessels also report that they rarely see a humpback in these months, but H.M.N.Z.S. “Lachlan” encountered six to eight near Pegasus Bay in November, 1952,
The decreasing incidence of sightings south of East Cape and scarcity of them along the east coast of the South Island certainly indicates that the majority of the whales travelling between North Cape and East Cape do not follow the coast closely once past the latter point. A course due south from East Cape would take the whales close to the Bounty Islands, so it was of considerable interest to receive reports of humpback schools sighted in this area from the “Alert” by Mr. A. J. Black and a scientific party he was transporting in November, 1950. Dr. R. A. Falla and Messrs. R. K. Dell and G. Turbott all described a steady stream of humpbacks sighted first at daybreak on November 11, when the vessel was about five miles west of Bounty Islands. For three hours when travelling slowly in fog to make the landing, humpbacks moving south were seen all round, and while there were no sightings during the time the party was ashore, they again entered the stream of whales at 1700 hrs. when they came off the island. During the three hours until darkness the vessel moving west towards Dunedin was passing through humpback groups of six or seven at a time, and the estimates of whales seen in the three hours vary between 50 and 100 humpbacks. There is no reason to doubt that the whales had been travelling in a similar density all day while the party was ashore. This represents a greater concentration of humpbacks than sighted in any other part of New Zealand waters with the possible exception of south-bound whales passing Centre Island in Foveaux Strait, and it certainly shows a different pattern to the more diffuse sightings recorded for humpbacks passing along the New Zealand coasts.
The easterly direction of whales sighted from Cape Reinga suggests that these travel along the east coast of the North Island as described above, but south of Cape Reinga some humpbacks travel off the west coast of the North Island (Fig. 2). Fewer are seen than on the other coast, and lighthouse returns from September to December are all negative, but Mr. W. W. Wellington, when on coastal vessels in this area, reported humpbacks in this season between Cape Maria Van Diemen and Manakau, and occasional whales (numbers unspecified) 2–10 miles west of Onehunga. South-bound humpbacks have been seen breaching by aircraft passengers passing along the coast near Dargaville during early November. Mr. R. C. Rutherford, who has fished regularly between Kawhia and Cape Egmont for 20 years has reported numerous sightings of humpbacks at this season between two and six miles offshore, travelling singly or in pairs, and on two occasions in groups of four or five. At his northern limit between Kawhia and Mokau he sights them regularly each year and at the same distance from shore they are seen travelling until south of New Plymouth. A group of three south-bound humpbacks 10 miles out to sea off Mokau in October, were reported by Mr. D. J. Holmes, of the trawler “Sirius”.
In the approaches to Cook Strait from Cape Egmont south, there is such a dearth of whale sightings that it is reasonably certain the majority of the whales do not pass through Cook Strait on the way south. A single humpback sighted from Stephens Island lighthouse in November and a cow and a calf travelling south past Porirua Harbour seen by Mr. C. Burns in the same month, are the only definite reports during four years' observations from this side of the Strait. The late Mr. J. A. Perano, of the Tory Channel whaling station, maintained a lookout for a season and found that although a few humpbacks were seen, there was no return migration through Cook Strait at all comparable with the northwards movement of May to August. Sporadic sightings such as those above and one seen in early November by the crew of the “Maimai” off Kaikoura on the south of the Strait, show that occasional humpbacks make the passage, and it is possible that it is some of these rather than humpbacks from round East Cape which are sometimes seen along the east coast of the South Island.
There have been no reports of south-bound humpbacks sighted from the only two lighthouses (Farewell Spit and Kahurangi Point) between Cape Egmont and Puysegur Point and the scarcity of sightings from the coastal vessels along the northern part of the west coast of the South Island indicates that very few humpbacks travel near the coast in this area. There have been two reports for October from near West Haven Inlet (crew of the Karamu) and two from about five miles west of Westport (crew of Kokiri), but all the sailors and fishermen whom I have interviewed from this coast have agreed in their comments on the rarity of whale sightings in these waters as compared with most other New Zealand coastal waters. However, as the majority of the humpbacks certainly avoid Cook Strait it appeared evident that those seen earlier north of Cape Egmont must travel off the west coast of the South Island but apparently too far offshore to be regularly encountered in the lane of coastal shipping. This has been confirmed recently by Captains Hill and Skinner and the crews of vessels which travel between Auckland and Westport on a route which is further offshore than that followed by the Wellington to West Coast vessels. At distances of 20 to 50 miles from shore the former vessels frequently encounter south-bound humpbacks which do not appear to approach the coast closely until the Jacksons Bay area is reached. From Jacksons Bay southwards humpback sightings have been reported regularly, as lone whales, pairs, or schools of 20 or more during the October to January period.
Crews on all vessels working from Dunedin round to Milford Sound between October and January have remarked on the large numbers of humpbacks seen between Milford Sound and Centre Island. Captain L. D. Williams, master-manager of the Foveaux Strait ferry vessel “Wairua”, has summarised as follows: “From observations during the past six years during the period mid-October to the end of November, large numbers have been seen during the ‘Wairua's’ voyages between Bluff and Milford Sound. Their movement is south along the west coast of the South Island, then travelling east to as far as Centre Island, thence south again along the west coast of Stewart Island. Very seldom is a whale seen on trips between Bluff and Half Moon Bay.” He has informed me that the majority are seen between three and five miles and greater distances off the coast, and other fishermen have stated that south-bound humpbacks are usually several miles out from Puysegur Point, which probably explains the fact that returns from the lighthouse there record only two humpbacks in this season, in contrast to their frequent sightings between May and August. A servicing party visiting the lighthouse in late October stated that large numbers of humpbacks were spouting around the vessel for as far as the eye could see on the day the vessel approached Puysegur Point. Mr. A. J. Black encountered similar concentrations offshore from Dusky Sound during a visit in November.
Instead of continuing due south past Puysegur Point, very large numbers of humpbacks turn due east towards Centre Island, and the numbers reported in this area are so great that it is evident that they are more than the continuation of the same group noted off the west coast north of Cape Egmont. Although they presumably incude most of this group, the majority of the south-bound humpbacks in this area apparently approach the New Zealand coast for the first time at points along the southern portion of the South Island west coast.
During four consecutive seasons, south-bound humpbacks have been seen from Centre Island lighthouse and described in similar terms by at least three different groups of keepers. In each case the whales were first seen in early October, and in two seasons small groups of from four or five up to 20 were seen per day with no sightings at all on a few days, while in the other two seasons this was interspersed with days during which humpbacks were noted in schools of 100 or more. In 1948 a school extending approximately seven miles by 25 miles with spouts too frequent to count was described. The principal keeper made an estimate of 200 to 500 whales,
and described his estimate as conservative. On three succeeding days the estimates were 40–50, 20–30, 20–30, and in each group many of the whales appeared to be feeding. In 1949 a concentration which was travelling past the island all day occurred on October 25, and it was claimed that the numbers were too great to estimate, while on October 22, 1953, Captain L. D. Williams noted 30 whales at one time in the immediate vicinity of his vessel.
During November, schools which were too large to be counted occurred on some days in all four seasons, and the data for one such month (in 1949) are listed below as an indication of the humpback groupings at this time:
1st, 31 sighted in schools of 3 to 10.
7th, 8 sighted.
9th, 40–50 sighted in schools of 8–12.
10th, 25 or more in one large school.
11th, 2 sighted.
14th, large herd sighted, 31 spouts counted in 15 minutes.
17th, 5 sighted.
18th, 4 or more sighted.
21st, 20 or more sighted in small schools.
22nd, whales sighted throughout the day. No count possible.
23rd, whales sighted throughout the day. No count possible.
24th, 50 sighted.
26th, one school of 5 and one of 3.
The principal keeper commented, “No regular watch was kept, and the number of whales reported are conservative”. Many of the above whales were noted as feeding, and large numbers of muttonbirds (Puffinus griseus) were often associated with the whales and feed.
In 1955 the support of the New Zealand Marine Department made it possible for the writer to spend a period in November making some observations in western Foveaux Strait during whale marking. Messrs. Perano Bros. co-operated fully by using one of their 35ft chasers for this work. Although periods of wind and high seas often made it impossible to operate in Foveaux Strait during the three weeks that the vessel was present, on the two full days plus four incomplete days spent on the western approaches to Foveaux Strait, approximately 300 humpbacks were counted from the chaser, and of these 106 were marked. All counting was done from the deck of the chaser, so that eye level was not more than about 8ft above water level, and it seems probable that many more humpbacks were in the general area on each of these days than we recorded. The humpbacks were mainly in groups of six to 12 or more and were often separated from the neighbouring groups by several miles. Some pairs and a few lone whales were sighted at the beginning of November, but in mid-November the schools appeared to have broken up and most of the humpbacks seen were in pairs or alone. However, this apparent breaking up of schools may have been brought about by the repeated movements of the chaser and the marking activity. Many of the whales were observed circling about slowly and feeding in patches of plankton, since identified by Dr. B. M. Bary as Nyctiphanes australis. In most of the small whale groups one or more calves of approximately 22 to 25 feet in length were present.
The observations during this period of whale marking are in close agreement with those which had been provided by many sources in other seasons, and confirm the presence of much larger daily totals of humpbacks in this area, than has been recorded near any other portion of the New Zealand coast. It is, however, possible that a proportion of the humpbacks remain for several days or perhaps longer in this locality as one humpback with a protruding marker and another with an unusual and distinctive colour pattern were sighted again in the same general area two and four days respectively after they were first seen. If a considerable proportion of the hump-
backs behave in this way then many would be re-counted on different days and the actual total passing the area would be less than that indicated by estimates derived from daily counts. At present there is no data to indicate the proportion of humpbacks which remain for more than a day in Foveaux Strait or any other areas along the New Zealand coast.
During December there is usually a substantial decrease in daily sightings, although in 1949 more than 100 were reported before December 14, which was the latest date for humpback sightings in that season. There have been sightings until mid-January during one season only.
Although many of the humpbacks trend eastwards for a number of miles past Centre Island they all appear to turn south eventually instead of passing through Foveaux Strait, and they then travel along the west coast of Stewart Island. Humpbacks are very seldom sighted from the “Wairua” during its many passages back and forth across the Strait or from fishing vessels in this area. None were reported from Dog Island lighthouse on the eastern side of the Strait during four years' observations, nor were any noted as passing through Foveaux Strait by Mr. Perano or the writer during the period of whale marking in November.
A number of observations which cannot be fitted into the migration pattern will be discussed under this heading. During January, February and March there have been reports of solitary humpbacks or pairs between North Cape and East Cape (17 reports), near Castlepoint (four reports), from Cook Strait (eight reports), and near Kaikoura (four reports). The only “out of season” concentration of humpbacks observed regularly has occurred during March on five successive years about 12 miles east of the Waitaki River mouth—i.e., in the Canterbury Bight. In the five years 1949–53, Captain J. Black of the “Taiaroa” recorded whales in this month, the earliest being on March 4, 1950, when about 12 humpbacks were seen cruising about.
Approximately six to 20 or more were seen on each day's fishing in the area until the beginning of April, so presumably it was a group which remained in the same area for about four weeks. His description and that of his crew left no doubt that the whales were humpbacks, and all the crew described the whales as moving about slowly in a small area feeding. During this month fish were especially abundant and all full of “small, clear shrimps with prominent eyes”, so the feed was evidently not Munida.
A concentration for a shorter period during 1954 was reported by Mr. C. Mark, of the “Waikawa”, who encountered four humpbacks between Whale Island (Bay of Plenty) and Cape Runaway on the morning of March 28, and then 17 more, including one calf, later in the day. All were cruising about slowly, and some at times lay on their sides with a flipper out of the sea. When back in the area on April 8, Mr. Mark encountered five humpbacks at the same position, but they appeared to be moving in a northerly direction at this date. Later in the month Mr. G. Mark, of the “Aorangi”. encountered a number of humpbacks feeding about four miles N. N.E. of Whale Isand. The school was noted first on April 27 and was still present on April 30. On both dates the whales were “apparently feeding on the large amount of anchovies that were on the surface”. On May 1 only three humpbacks were seen, but on May 6, 7 and 8 there was an association of seabird flocks, and many (i.e., more than 20) humpbacks apparently feeding on small fish. Mr. Mark stated that “they are definitely found to be feeding amongst the large groups of birds which are feeding on ‘anchovies’ which come to the surface in millions. When the whale reaches the surface I have seen these anchovies all bounce off the backs of the whales. The birds do not have to dive for the feed as it is on the surface, and the whales take the fish on the surface—just plough round
amongst the birds.” On May 9 the fish shoals were less prominent, and only one humpback was sighted. On May 10 he reported “no humpbacks, birds or anchovies”.
As these groups were not reported as seen during their approach or departure from either the Waitaki River area or Bay of Plenty, there is no data to indicate whether they were very late south-bound whales, early north-bound whales or groups which had not proceeded in the usual migration route.
Records of coastal sightings are too diffuse except for those from the south-west corner of the South Island to be used as a basis for comparing differences in the duration and season of migration, or the relative abundance of humpbacks passing fixed points in different years. Records from the Tory Channel whaling station give information on these topics for north-bound humpbacks passing through Cook Strait during 36 seasons while those from Whangamumu give comparable data for three seasons together with data on south-bound humpbacks during two seasons. The whales seen from Tory Channel lat. 40° 10′ S. are a sample of those coming up the east coast of the South Island and passing through Cook Strait to travel west of the North Island. Whangamumu at latitude 35° 2′ S. is six degrees further north and whales seen in this area are a sample of those which have remained to the east of both islands of New Zealand but which would probably be part of the same stock as those seen in Cook Strait. In both these areas the seasonal data is that obtained by professional whalers maintaining lookouts from hills during each season and the only major factors which may confuse the records are differences in weather and in the intensity of scanning. Although the records of humpback sightings from Centre Island (latitude 46° 25′ S.) undoubtedly form a less complete sample of those passing the area than is the case for Cook Strait and Whangamumu, sufficient data were obtained to show the periods of migration past the south-west corner of New Zealand. Humpbacks which pass Centre Island approach and leave New Zealand coastal waters within relatively short distances of Centre Island and form a local stream leaving the west coast of the South Island on a course separate from those passing through Cook Strait or near Whangamumu (see Figs. 1 and 2). Nevertheless as all three groups are presumably parts of the same main stock, the data allow some comparisons between the migration periods at the three latitudes. The data will be discussed as follows: Cook Strait, Whangamumu, Centre Island.
A. Cook Strait.
The number of humpbacks sighted per season for 32 of the seasons between 1914 and 1955 is shown in Table I. The data on sightings during each of the seasons prior to 1940 have been obtained from diaries loaned by Miss M. Toms, of Pauahatanui, while those for 1944 to 1955 have been provided by Mr. G. T. Perano, who also supplied day to day catch returns back to 1929. Diaries for a number of seasons have not yet been located, and those for 1926 and 1927 listed all catches, but the few other sightings indicate that the latter were not all listed, while sightings are listed for 1914 but not the humpback catch. During the 1932 season operations were greatly reduced owing to the economic depression, and the lookout was maintained for a shorter period than normal and operated with fewer men.
For the other 28 seasons all sightings are recorded, totalling 4,161, averaging 148 per season, but there has been some difference in intensity of scanning throughout that time. In many of the early seasons the number of whalers scanning varied and as a very small plant was available for processing the scanning sometimes ceased for a day or so at a time or for parts of days when there were enough dead whales to keep the factory working to capacity. Binoculars were not used in the early seasons and attention was concentrated on waters within a short distance of shore. Despite this the number seen in some recent seasons—e.g., 115 in 1950, have been lower than in some of the early seasons—e.g., 154 in 1915 and 168 in 1920. However, the
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|Average of 13 seasons||25||23|
average number sighted over a number of seasons has tended to rise (see Table II), and for the decade 1944 to 1953 it averaged 173. During the 1954 season there was a spectacular increase to 495 sighted although the lookout equipment and personnel were essentially the same as had been used throughout the previous decade. Long spells of clear weather frequently made it possible to see a greater distance than usual, but there can be little doubt that humpbacks were considerably more abundant than usual in Cook Strait during 1954. This has been confirmed by a sighting total of 190 in Cook Strait during 1955.
A comparison of variations in the numbers and time of migration of humpbacks in the different seasons depends largely on the representativeness of those sighted as compared with the total humpbacks passing through Cook Strait each
season. Scanning is carried out from a lookout situated on a headland about 200 feet above sea level on the south-west side of the narrowest part of Cook Strait (i.e., 14 miles), and during average visibility spouts can be seen for a distance of at least nine miles. There is a permanent lookout man scanning the Straits from dawn till dusk and when not hunting, the six men who make up the chaser crews also take part. At the times that the catches are less than the factory can deal with, the towing vessel frequently leaves before daylight and sails up to 20 miles northwest by dawn to be in a position to sight whales which may have passed through the Strait during darkness. The whales which must pass unobserved are those which during darkness traverse the whole distance that can be scanned next morning from the lookout hill and sometimes the distance that can be scanned from the tug further north in addition. Although there are 14–15 hours of inadequate light for scanning, it would require several hours for a whale at the normal cruising speed of four to five knots to pass the area which can be seen next day. This reduces the effective cover to approximately nine hours or less in normal weather, but there are a number of days in each season where misty rain reduces visibility to almost zero, or gales confuse the surface of the sea to such an extent that spouts can be distinguished only when very close. Any estimate of the proportion which passes at these times or even travels unobserved in good weather would be highly speculative, but the height of the lookout, its situation at the narrowest part of the course into which all the local stream of whales have to be funnelled, and the number of experienced observers scanning Cook Strait make it probable that their sightings, although not large, represent a larger proportion of the local stock than would be seen from most whaling stations.
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|Seasons||Total seen||Total caught||% caught||No of seasons||Average seen||Average caught|
|1915–1920 (excluding 1919)||642||213||33||5||128||43|
|1928–1939 (excluding 1932)||1,107||641||58||11||101||58|
For a number of seasons (1940–1953) the dates of sightings were not recorded, but a record of the numbers for each of the seasons from 1944 was carefully kept by notches cut into one of the lookout chairs. Counts of these have provided the sighting data for 1944–1953, and from Table II it can be seen that catches during that time represented an average of 61% of those sighted. The dates for catches were recorded for these seasons and also for 1940–1944. In lieu of dated sighting data these have been used to give the main sequence for the 1940 to 1953 seasons. During those seasons for which there are dated records of both sightings and catches it can be seen from Fig. 3 that there is good agreement between the two sets of data excepting for a slightly higher ratio of sightings to catches near the middle of the season.
The time sequence and relative density of humpbacks per week for 35 seasons has been summarised in Fig. 3. The earliest and latest record in this period were May 2 and August 29 respectively, thus covering a period of 17 weeks, but Fig. 3 shows that the greater part of the migration through Cook Strait occurs in June and July. Approximately three-quarters of the total were noted in the seven weeks period June 12–July 30, with the highest weekly sightings from June 19–July 9. Fig. 3 indicates a tendency for humpbacks to pass through Cook Strait in small numbers early in the season, followed by increasing numbers per week until the peak period between mid-June and early July, followed by a decline in numbers
per week until the end of the season. Part of the apparent rise and fall in records per week as indicated by the combined weekly totals is due to the inclusion of seasons with a late start or early termination, but the individual seasons also show a gradual rise and fall, although with varying dates for commencement and termination.
The number of humpbacks sighted (or caught) per week during each of 36 seasons is listed in Table 3, which shows a very considerable weekly variation in nearly all seasons, although the tendency towards larger numbers at mid-season is apparent in nearly all cases. A more useful criterion for considering seasonal variation in time sequences, is to compare the time required in different years for equivalent proportions of each season's total to pass through Cook Strait. The proportions used are as follows:—Time intervals in days for 12½%, 25%, 50%, 75%, 87½%, and 100% of those recorded. This arrangement results in a growth increment curve for the population each season, but for convenience is shown in column form in Fig. 4. The commencement of each season's column is arranged against the date for the beginning of the season, so Fig. 4 also shows the dates on which each increment was reached, as well as the length of time required for each increment The peak is taken as the date by which 50% of the sightings or catch had been recorded, and
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|May||June||July||August||Total seen or caught|
Fig 4.—The dates in Cook Strait on which the following proportions of each season's total sightings were completed are as follows, reading from left to right: Commencing date (start of column); 12½% (end of stipple); 25% (end of lines); 50% (vertical white line); 75% (end of solid); 87 ½% (end of lines); 100% (end of column representing the end of season). For the seasons 1940–1953 (inclusive); the dates for proportions of catch only are shown. For the numbers of humpbacks per season, see Table I and text
the 25% on either side of the peak shows the time required for the central half of the migrating stock to pass through Cook Strait.
From Fig. 4 it can be seen that the individual seasons have varied in duration from 64 to a 110 days (averaging 86 days) and there is therefore no significant correlation between the start of the migration and its termination. The longest seasons, 1920 and 1937, commenced on May 2, which is earlier than usual but did not end until August 20, which is later than normal. In 1940 the season commenced more than four weeks later but ended a week earlier. There can, therefore, be no doubt that the whales sometimes travel in a more compact group which passes in a shorter period, while in some other seasons they are spread out as they migrate through Cook Strait and the period of frequent sightings may be prolonged. There is, therefore, no correlation between length of season and number of sightings or size of catch.
The date that the first sighting or catch occurred does not correlate with the peak of the season, which, as calculated above, varies through five and a-half weeks ranging from June 21 to July 29. As the date of appearance of the first whale may be followed by many days before the main group of whales commences to pass through the Strait, it is no consistent guide to the time that the main group of whales will pass through. In the most extreme case a whale was caught on May 20, in the 1934 season, but no more were seen during the next three weeks, and regular sightings and catching did not commence until June 11, although the weather had been suitable for sightings throughout that period.
Of all the intervals shown in Fig. 4 there is greatest variability in the quarter made up of the first and the last 12½%. It ranges from 16 days (in 1940) and 55 days (in 1949) to 69 days in 1920. In these cases the first 12½% was noted in four days in 1940, indicating a season where the main group of whales followed very closely after the first ones passing through the Strait, while 35 days elapsed in 1949 and 46 days in 1920 before the same proportion was observed. In most seasons the time taken for the last 12½% of the sightings tends to be shorter than the first 12½% because whaling ceases if the whales are becoming too widely spaced and there may be a few late migrants which pass through Cook Strait after the lookout has ceased. Even so there are six seasons in which the terminal 12½% of the records were spread over a substantially longer period than the first 12½%. If whales are widely spaced early in the season some of the whalers believed that this was a probable indication of a similar spacing at the end of the season. There are too many exceptions to this for it to be used as a guide to the distribution of whales later in a season. Seasons such as 1933 and 1943 commenced slowly but ended relatively quickly, while others, such as 1952 and 1953, commenced quickly, but Fig. 4 shows that the late whales were considerably more widely spaced.
It would be expected that the second 12½%, being closer to the peak of the migration, would travel in less time than the first 12½%, and this is the case in all except four seasons. The latter show the second interval of almost equal length to the first except for the 1940 season. In all seasons except 1917 the penultimate 12½% travelled through Cook Strait in less time than the terminal group.
The central half of the migrating stock is indicated as the two 25% groups on either side of the date for half the total sightings. There is closer agreement between the duration of each of these 25% groups per season than between any of the other intervals. In all except the 1915 and 1951 seasons, the interval occupied by the middle half of the migrating stock is substantially less than for the other half. The period ranges from 18 to 39 days, whereas that for all seasons combined is 32 days. In spite of the wide range of variation in the time taken by the various proportions of the migrating stock, the tendency for humpbacks to migrate in a group which is spaced out most widely at the van and rear and grouped more compactly in the middle is shown in all except two of the 35 seasons.
The central grouping as indicated by catch, is most spectacular in the 1942 and 1948 seasons, in each of which the middle half of the catch was taken in 18 days (see Fig. 4), whereas the total season lasted for 95 and 87 days respectively. The dates of sightings were not recorded for these two seasons. However, the ratio of catch to sightings is almost invariably lowered near the peak of migration because the factory is then working to capacity, and it is not possible to deal with the same proportion of those seen as can be done when the whales are more widely spaced. During these two seasons as well as the others between 1940 and 1953, the central half of the local humpback population probably traversed Cook Strait in a more compact group than indicated by the catch data alone. This was certainly the case in 1954, when 28 days were occupied in catching half the seasons's total, but as shown in Fig. 4 the central half of those sighted occurred in only 18 days. One hundred and twenty-five humpbacks, or more than a quarter of the total sighted, passed through Cook Strait in one week (June 26–July 2).
The two seasons, 1915 and 1951, which do not show the presence of a more compact central group, both had the highest weekly sightings early in the season, and the grouping into proportions of catch from the starting date as shown in Fig. 4 obscured the early concentrations in each case. It is clear, then, that all seasons have shown some period with a marked concentration of whales, and there has been no evidence of more than one such peak in a season.
In all seasons except 1915 and 1951 the maximum concentration has occurred near the mid-point of the central half of the sightings and therefore coincides closely with the date for the completion of the first half of each season's sightings. This date is calculated from the total seasonal data, and is dependent on the distribution of the whales throughout the season, whereas the commencing or closing dates for a season can be substantially altered by the presence or absence of a single whale. The date for the mid-point of sightings or catch will not be varied greatly unless the whole whale group is moving through Cook Strait earlier or later than usual. The mid-point has therefore been selected for comparing the times of humpback migration in different seasons. It shows a fluctuation through a maximum interval of 38 days between June 21 (1947 and 1950) and July 29 (1933), whereas the equivalent point for all seasons combined is July 5. Some of the smaller differences in the time of the apparent peak in different seasons are caused by variations in the length of adverse weather conditions which have prevented the sighting of some of the whales passing through Cook Strait. Such periods of unfavourable sighting conditions lengthen the period required to record a particular proportion of the catch, and result in an apparent shift for the date of the mid-point or peak of total sightings.
The factors determining visibility from the Tory Channel lookout are so frequently localised and subject to rapid change because of the unstable meteorological conditions in the Cook Strait area that it has not proved possible to use the weather records from the nearest meteorological station as a sound basis for correlating the distribution of sightings with weather. It is unlikely, however, that a range so large as 38 days in the time of the peak could be due solely to local weather conditions. It is more probably a real indication that the date of movement for the main group of humpbacks does vary considerably.
The cause is not apparent, but may well be due to annual differences in climate at the site of the beginning of the migration resulting in an earlier or later start, which is reflected in the variations noted at Cook Strait Records from the latter area illustrated in Fig. 4 show the seasons which have been early or late as compared with the average for 35 seasons, but there is no indication of the factors which may have affected the time of the migration movement in the different seasons. There are also no regular cyclic sequences of seasonal patterns recognisable from the available Cook Strait data. However, the fluctuations evident in Fig. 4 show some sequences
of seasons in which the time of movement of the central portion of the humpback stock becomes progressively earlier or later for a number of years in succession.
There is much less information on sightings off this locality than for Cook Strait, and for most seasons a record of catch is the only specific data still available. The number of humpbacks caught from Whangamumu per season between 1912 and 1931 is shown in Table I. For these years the humpback catch totalled 963, with an average of 48 per season, and the catch of other species was negligible. Although whaling with a steam chaser and explosive harpoon commenced in 1910 the diversion of the vessel for periods during the first two years to test other areas reduced the catching period from Whangamumu during the 1910–1912 seasons. Prior to 1910 humpbacks had been caught in steel nets in small numbers only, and from 1890 until the cessation of effective whaling in the area in 1931 the total humpback catch would not greatly exceed 1,000 whales.
Until the power driven chaser was introduced whaling was confined to the June to August season and included only north-bound humpbacks, but from 1912 onwards whaling was carried out in two seasons each year and both north-bound and south-bound humpbacks were caught.
The totals as recorded by the New Zealand Marine Department gave no indication of the relative density of the two migrating groups, but through the courtesy of Mrs. D. Cook, of Russell, who allowed me to examine account books held by her, it was possible to calculate the size of the catch from each group from the bonuses paid to gunners in each of the winter and spring seasons in the years 1919–1931. Of the 635 humpbacks caught in these twelve years, 333 were from north-bound whales caught in the winter months and 302 from south-bound whales caught in the spring months. This shows no significant difference in the size of the catches from each of the migrating groups, and as can be seen from Table I the greater number of whales occurred in either the winter or the summer seasons at random.
It is not possible to use these figures as a basis for comparing the density of humpbacks passing this area with those passing Cook Strait, as a single steam chaser only was used for many of the seasons at the former, and an average of three high powered launches from the latter, while the hunting techniques were also somewhat different in the two areas. The only available data that can be used for comparison are the records of sightings for three winter and two summer seasons as recorded in a log for 1898 now held by Mr. G. Cook, Auckland, and for the 1930 and 1931 seasons from logs held by Mrs. D. Cook, of Russell. These record the following: For winter seasons 1898, 117; 1930, 51; 1931, 108; and for summer seasons 1930, 64 plus three suckling calves; 1931, 74 plus 14 suckling calves. Logs for the intervening years have unfortunately been destroyed. The little data available show, however, that the size of the north-bound humpback population passing close to Whangamumu is not strikingly different from that passing through Cook Strait. Although the sighting records suggest that the size of the south-bound group is smaller than the north-bound group at Whangamumu, the catch data for 12 seasons discussed above show that over a longer period the difference was slight, whereas the Cook Strait data show that few humpbacks pass through the latter area on their south-bound migration.
Commencing dates for the three winter seasons recorded were June 10, 18 and 12 respectively, the mid-point for sightings in 1898 and 1931 were July 8 and July 28, while the last sightings of north-bound whales occurred in these two years on August 2 and August 25. Although these data fall within the same time range as for some of the seasons at Tory Channel (see Fig. 4), ex-whalers from Whangamumu state that the seasons usually commenced about one to two weeks later than Tory Channel in any one season. The mid-point for the two seasons combined is July 12.
The sightings of south-bound whales in 1930 and 1931 commenced on September 20 and October 1, the mid-point for both years was October 20, and the last whales were seen on November 8 and November 17, and ex-whalers state that the latest date on which they saw a whale in any season was December 11. The number of humpbacks recorded at Whangamumu per fortnight for both winter and “summer” seasons during the above years is shown in Fig. 5.
C. Centre Island.
Records from this area have been made under such different circumstances from those at Tory Channel and Whangamumu that it is not feasible to compare the numbers closely with those recorded at the latter localities. No continuous watch was kept and the lighthouse keepers were not trained whale observers. In spite of these handicaps, the number of whales reported by them was so large, as compared with elsewhere along the New Zealand coast, and the records were kept for a sufficiently long period (four years), to give useful indications of the seasons for humpback movements past the south-west part of New Zealand.
During four seasons the northward migrants were first seen near Centre Island on or about May 10 and continued steadily until mid-July, when a decrease in numbers per day occurred and lone whales only were seen until these had also passed the area by early August. The mid point for 218 whales recorded during these months was June 15.
South-bound humpbacks, during the same four years, were first recorded between October 2 and October 6, but did not occur as a steady stream until approximately October 20. From that date until late November the greater part of the sightings were made, and except for “stragglers” the last humpbacks were sighted between December 9 and 14. Approximately 1,500 humpbacks were recorded for these months in four years, and the date on which half the sightings had been completed was November 8. The 300 counted in six days during November, 1955, are not included because the observations made at that time covered too short a period to indicate the duration and scale of movement in that year.
The most striking feature of the humpback migration past this area is the great difference in the numbers passing when north-bound as compared with the numbers passing when south-bound. From Fig. 5 it can be seen that although the period during which north-bound humpbacks are observed near Centre Island is longer than that for south-bound whales, approximately seven times as many have been recorded in the latter period as in the former. Part of this apparent increase may be caused by the re-counting of whales which remain relatively stationary in the area for several days as described earlier. However, the large totals frequently recorded in separated groups on any one day are also much greater than any noted during the north-bound migration, and it is evident that considerably more humpbacks traverse the locality when south-bound than is the case when north-bound. It may be largely the resut of a cumulative effect from whales approaching the west coast at various points and then all being deflected into the same area by the southwest trend of the coast.
The likelihood of such a cumulative process during the northward migration along the east coast of New Zealand has been discussed, and it was also pointed out that a considerable proportion of the humpbacks pass through Cook Strait and others may leave the coast beyond East Cape. Consequently those sighted near the northern end or any other part of New Zealand represent only a portion of the stock which approach the whole east coast of New Zealand. Of the south-bound whales reaching the west coast of New Zealand, only a negligible proportion pass through Cook Strait and there is no headland comparable with East Cape from which humpbacks leave the west coast until the south-west corner of the South Island is reached. Therefore the humpbacks seen in the latter area represent almost the entire accumulation along the west coast of both islands of New Zealand, whereas the much smaller
north-bound group seen in this area represents only those which have approached from the open sea in the south into the immediate vicinity of the south-west corner of New Zealand.
By comparing Figs. 1 and 2 it can be seen that many of the humpbacks return via a different route from the one they followed northwards, and it is probable that a high proportion of those which travelled north along eastern coastlines return near the western coasts, and therefore contribute to the concentrations which occur at the south-west corner of New Zealand. Further whale marking in the latter area is probably the only procedure that will make it possible to confirm that some of the humpbacks which travel northwards along the east coast return via the west coast. The available west coast data suggest that the majority first approach the coast towards the southern half of the South Island rather than by equal increments along the whole coastline, but more evidence from this sparsely populated coast is required. In view of the very great difference between the numbers recorded near the south-west corner of the South Island and those in any of the groups recorded from New Zealand for north-bound whales, it is at least possible that some of the former include whales which migrated north along some route other than along the New Zealand coast.
Eleven degrees latitude separates Centre Island (46° 25′ S.) from Whangamumu (35° 20′ S.), so the differences in time sequences for the passage of north-bound and south-bound humpbacks at these localities provides a basis for some estimate of migration rate. The sequence of movements in these two regions are most readily recognisable when the fortnightly totals in each are arranged as cumulative percentages of the total number of humpbacks recorded in each area, as shown in Fig. 6. The left hand curves show the total percentage of north-bound humpbacks which have passed the area at the end of each fortnight so that the point for 100% shows the time by which all have passed to the north. The right hand curves show the percentage still remaining in the north at the end of each fortnight until at 0%
all have returned to the south. For both north and south-bound migrations the major portions of each curve for the two areas are approximately parallel and therefore follow similar sequences, but with different commencing dates.
The actual dates for either north or south-bound migrations cannot be compared closely as the data for the Whangamumu apply to different seasons from those recorded at Centre Island, and it has already been shown from Cook Strait records (Fig. 4) that the dates for the passage of different proportions of the humpback group vary considerably from season to season. However, this should not affect the validity of a comparison between the periods required for the overall cycle of south to north and north to south migrations past each of the two localities. From Fig. 6 it can be seen that the cycle from commencement to termination takes approximately eight weeks longer at Centre Island than at Whangamumu, but the interval between the mid-points of each of the curves is rather less. The actual dates of peaks calculated from the daily returns (as previously described for Cook Strait seasons) are June 15 and November 8 for Centre Island, and July 12 and October 20 for Whangamumu. Hence this cycle takes approximately 20 weeks at Centre Island and 14 weeks at Whangamumu.
The difference of six weeks should represent the time required for the main peak of the humpback migration to pass through 22° latitude made up by the 11° latitude northwards from Centre Island to Whangamumu and later back southwards through the same distance on the return passage. This indicates a relatively slow rate of progression averaging less than four degrees latitude or about 220 nautical miles per week in a direct north and south line. The cruising rate of humpbacks on passage observed by Chittleborough (1953) averaged 4–5 knots, and the writer has had many experiences when whale marking in Tonga from a 5-knot launch, of maintaining the same relative distance from a humpback or gaining on it only very slowly, so that the whale's speed agreed with Chittleborough's data. On the other hand, some of the humpbacks in Tongan waters could be seen circling slowly or stopping in the same general area for hours on end, and so long as they were undisturbed the forward progression in any one direction was slight. Similar behaviour has already been described for humpbacks feeding in western Foveaux Strait, and movements of this type have usually been regarded as a feature of their behaviour only after the breeding or feeding areas had been reached. The great difference in rate between 4–5 knots and little more than 1 knot in the overall rate of advance described above, indicates that there are frequently periods of rest and random movements on quite a large scale in the course of their main migratory route.
An interesting capture of a humpback at Tangalooma only six days after it was marked about 500 miles away at St. George's Head, New South Wales (Robins, 1955) shows that humpbacks sometimes travel for considerable distances at relatively high speed. However, the present data indicate that comparable sustained speed is not typical of the main group of migrating humpbacks which passes New Zealand.
The period of peak concentration at the breeding grounds north of New Zealand can be inferred from the Centre Island and Whangamumu data. The latter shows that the last of the main northbound group leave New Zealand in late August, and in most seasons there is a period of nearly four weeks before the first of the returning south-bound humpbacks are seen. The peak of the concentration at the northern limits probably occurs about midway between the dates of departure and return or between the peaks of the north-bound and south-bound migrations past New Zealand. For the Whangamumu data the former date is September 7 and for Centre Island during seasons other than those used in the Whangamumu records, it is September 9, but as the dates midway between the peaks of the two migration streams past Whangamumu and Centre Island are August 30 and 26 respectively, the beginning of September can be taken as the approximate time of the peak concentration at the breeding grounds. At Point Cloates (lat. 20° 30′ S.), West Australia,
Chittleborough (1953) found almost equal numbers of whales moving northward and southward close to August 24. Presumably the peak concentration is then at the northern point of the migration with equal proportions coming to or leaving that point. There was some overlap of north-bound and south-bound whales at the latitude of Point Cloates for approximately 10 weeks, whereas it is rare although not unknown for south-bound whales to reach New Zealand latitudes before the last of the north-bound whales has departed.
The tropical regions north of New Zealand already known as centres of humpback concentrations are Tongan waters and the Coral Sea, which both extend north to at least 15° S., and there is evidence that some humpbacks travel considerably further north, although probably not so far in a compact group as do the South Atlantic humpbacks which form a breeding concentration near the equator in the Congo area. Most of those passing Centre Island probably travel between 30 and 40 degrees further north and then back again in a period of not more than the 20 weeks between the peaks of north-bound and south-bound migrations past Centre Island. Similarly those passing Whangamumu probably travel north between 20 and 30 degrees and then return the same distance within 14 weeks.
There is no direct evidence of the period spent in one place in the tropical waters, but the frequent observations of slow movement in apparently random directions, or breaching and other behaviour in the one spot in warm waters, does indicate at least some time spent in the general area before migration is resumed. If the migration rate during passage remains approximately the same as in the 11° of latitude traversed along the New Zealand coast in three weeks, the peak of the migrating group would be expected to travel between northern New Zealand and 15° S. and return in about six weeks, or even to latitude 5° S. and return in less than 12 weeks. Depending on the distance travelled, the average period spent by humpbacks at the breeding ground probably varies over a period of the order of two to six weeks and is certainly very much shorter than the period spent on the southern feeding grounds.
The greatest humpback concentrations on the feeding grounds in Area V have been encountered near the latitudes of the Balleny Islands, which are 20° S of Centre Island. From the dates of peaks at Centre Island and the rate of progression past New Zealand, the main stock would be expected to have left the southern concentrations by the beginning of May and to have arrived back between mid and late December, thus allowing a period of four to five months at the southern end of the migration route. These times relate only to the hypothetical mid-point of the migrating stock, so as there is a spread of approximately six to seven weeks on either side during the period that whales pass New Zealand, the time of departure and return for the beginning and end of the migrating stream at each locality would be correspondingly modified.
The seasonal duration of sighting records on north-bound whales at Centre Island, Whangamumu and also Tory Channel, average approximately 12 to 15 weeks, while that for south-bound whales at Whangamumu and Centre Island is only 8–10 weeks. This difference could be caused either by a difference of speed in the migration or in the relative spacing of the individual animals resulting from greater or less spread in the departure times. There is no New Zealand data to show which is the more probable alternative, but if there is little variation from the overall rate of progression past New Zealand, then the spread of the north-bound migrating stock at its maximum extension would include more than 40° latitude, and the south-bound stock approximately 30° latitude. A greater speed would increase the latitude spread or result in some humpbacks having arrived at one end of the migration route before others had departed from the opposite end.
A hypothetical reconstruction of the cycle followed by the central portion of the migrating stock, expressed in very general terms, is as follows: After departure fromx
Fig. 6.—The cumulative percentages of humpbacks which are to the north of Centre Island, Whangamumu, and Tory Channel at the end of each fortnight. (See text.)
approximately latitude 66° S. by early May it reaches latitude 46° S. by mid-June, and travelling at the rate of about 220 nautical miles per week then passes latitude 35° S. three weeks later before reaching the breeding area in latitude 15° S., in early to mid-August. Here or perhaps further north there is a period of two to six weeks in the tropical waters before departure south, so that the peak is in latitude 35° S. between mid and late October and at latitude 46° S. by early November. The arrival back at the feeding grounds is caculated as mid- to late December, which allows a period of four to five months in this area. The corresponding dates for the earliest and latest humpbacks in the migrating stock are probably six to seven weeks earlier and later than those calculated above.
There is much evidence that humpbacks migrate through coastal waters more frequently than do other species of whale. The history of the effects of inshore whaling on the total stocks shows that a very high proportion of the total humpback stocks come close to shorelines. Humpback catches from shore stations or factory ships operating near shore at South Georgia and the West African coast had so decimated the humpback stocks of Area II even before pelagic whaling proper had started to extend the hunting from coastal into oceanic waters, that humpback stocks in this area have still not recovered. Ruud (1952) and Budker (1953) have shown that after each of several periods of three to five years' operations, the humpback catches near the coasts of the Congo and Western Australia have also declined markedly. This can be explained only by assuming that a high proportion of the stock were congregating close to the coastal whaling areas each season.
Considerably more humpbacks have been caught from southern hemisphere shore stations than from pelagic whaling (Dawbin 1952, p. 187). Part of this has been due to gunner selection and later protective regulations for humpbacks in Antarctic waters, but Mackintosh (1942) showed that immediately before World War II humpbacks were considerably less abundant in the Southern Ocean than fin whales, and probably less than blue whales. The proportions indicated by Mackintosh's data were, humpbacks 5 to 15 per cent., fin whales 65 to 85 per cent, and blue whales 10 to 20 per cent. These ratios were calculated for summer months when the whales congregated in the Antarctic feeding grounds, so they presumably indicate the relative abundance of these species in the southern hemisphere as a whole. Nevertheless the catch of baleen whales from tropical shore stations has been mainly humpbacks, suggesting that fin and blue whales either do not go so far north or do not come
close to shore in these latitudes. In the subtropical zone blue and fin whales as well as humpbacks are caught from most of the African and South American stations, with fin whales markedly predominant, but from the Australian and New Zealand stations humpbacks only are caught most seasons. Near the Point Cloates station (West Australia), aerial surveys described by Chittleborough (1953) located several hundred humpbacks, but only 19 fin and blue whales. Even fewer fin and blue whales are encountered in waters near Moreton Island (East Australia), while sightings in New Zealand waters during the winter months are almost exclusively of humpbacks. In Australian and New Zealand waters humpbacks clearly accumulate along parts of the coast while fin and blue whales either avoid the coastal waters entirely or travel sufficiently far from shore to be sighted only rarely.
Factors affecting coastal migration route.
The available data on the route followed by humpbacks in New Zealand waters shows that they seldom approach close to certain sectors of the coast, but that large numbers pass inshore at other regions such as the south-west corner of the South Island. The regions approached or avoided differ in a number of respects for the north-bound as compared with the south-bound humpbacks. These two facts strongly suggest that one or more, probably a number of local factors operate which affect the route followed by the migrating stock. The possible part played in this connection by the following will be considered separately:
(1) Direction of coastline.
The east coast of New Zealand shows a continuous north-easterly trend as far north as East Cape. North-bound whales approaching any portion of the coast to the south of this point are necessarily compelled to continue in a north-easterly direction except for those which pass through Cook Strait. Beyond East Cape the coastline has a general west or north-west trend, and whales in this region can move freely in any direction within the northerly quarter. Nevertheless the majority continue to follow the trend of the coastline closely through Bay of Plenty and off North Auckland until the northern tip of New Zealand is reached.
Those which pass through Cook Strait must necessarily move in a north-westerly direction until they reach the vicinity of Cape Egmont, from where they could travel in various directions within the northerly quarter. It is apparent from the scarcity of sightings along the remaining portion of the North Island coast that the majority continue to move in the north-westerly quarter, and few come close to the coastline again north of Cape Egmont. A similar north-westerly trend away from the coast-line is followed by the stocks which reach the Jackson's Bay area after following the west coast of the South Island as far north as that area.
In the New Zealand coastal waters considered as a whole the north-bound humpbacks show a definite trend towards the north-west in all those areas where there is freedom of movement to any part of the northerly quarter, and this occurs whether that trend is along or away from the coastline. Where the coastline has a northeasterly trend the humpbacks appear to desert it unless the coastline lies across their pathway.
Southbound humpbacks encountering any portion of the coast between North Cape and East Cape are deflected by the coastline towards the south-east before it is possible for them to continue steady migration in any other part of the southerly quarter. They are therefore observed frequently near the coastline as far as East Cape, but south of this point the coast trends towards the south-west and very few south-bound humpbacks are seen along it even though it is a coastline followed earlier in the season by many north-bound humpbacks. Apparently most of the whales continue due south or possibly south-east on a course which takes them away from the coastline south of East Cape, and the only record which possibly represents a part of their further course is the concentration described near the Bounty Islands.
Along the west coast of the North Island the sightings for the south-bound whales are more numerous for the section down to Cape Egmont than they are for those north-bound earlier in the season. Although the numbers are not large it is clear that there is a regular movement along the south-easterly trend of this coast suggesting that the whales came in from the north-west as any from the north-east or even due north would be largely obstructed by the presence of intervening land. However, there is very little evidence of humpbacks resuming the south-easterly direction beyond Cape Egmont, as this course would bring them through Cook Strait, and it is certain that very few south-bound whales pass through these waters. The reasons for the avoidance of Cook Strait during the southward migration are not yet apparent, but once it has been by-passed the direction followed by those moving past the South Island must be south-westerly as far as Puysegur Point, and even then the humpbacks travel well offshore until the Jacksons Bay area is reached. From Jacksons Bay southwards the humpbacks not only travel close to shore to Puysegur Point but continue to follow it closely in an almost due easterly direction towards Centre Island, and the steady augmentation of numbers between those localities strongly suggests that many south-bound whales first encounter the New Zealand coast in this area. At Centre Island all turn sharply to the south-west, thus avoiding Foveaux Strait, and so pass along the west coast of Stewart Island.
South-bound humpbacks in general, therefore, closely follow only those coastlines which are across the path of their approach from the north or north-west, and their course largely by-passes the whole east coast of New Zealand south of East Cape. In addition they avoid passing through either Cook or Foveaux Straits, although the westerly approaches of both are traversed.
The routes followed in New Zealand waters cannot be explained merely in terms of preference for moving close to any available coastlines. Most of the sectors which are followed closely are only those that lie across the path of their main south-north or north-south migration routes. The fact that there are indications of trends towards the north-west and south-east during these movements serves to increase this effect, as approaches from these directions are almost at right angles to the longest axis of New Zealand, and so increase the effective width of land across their migration pathway.
(2) Oceanographic factors.
Such properties of the individual water masses as temperature and salinity are unlikely to be major factors in modifying the migration route of humpbacks as they traverse the widely differing Antarctic, sub-Antarctic and sub-tropical water masses in differing proportions according to the route followed by each of the major whale groups in the southern hemisphere. The direction of current flow appears also to be unimportant as the known south-north movements of humpbacks in the southern hemisphere along the coasts of each of the main land masses shows that some groups move in the same direction as northward moving cool currents—e.g., off West Australia, West Africa and Western South America, in the West Australian, Benguella and Humboldt Currents respectively, while others at the same phase of their migration travel against southward moving warm currents—e.g., off East Australia, East Africa and Eastern South America in the East Australian, Agulhas and Brazil Currents respectively. The reverse applies in each case during the north to south migration. The general direction and season of humpback migrations are therefore much the same throughout the southern hemisphere regardless of the physical properties and direction of flow of the water masses traversed en route.
Townsend (1935), after plotting the distribution of nearly 54,000 whales of various species, including 2,883 humpbacks, referred to studies on the effects of ocean currents on whale movements and stated that “the present writer, after much study of oceanographic literature, abandons his attempt to set forth what is known
of their relationship”. Harmer (1931), when referring specifically to water temperature, concluded that the direct effects of variations of temperature are probably not important in the case of adults at least. He suggested that any apparent correlation between the location of whales and temperature is not solely due to their preference for water of a particular temperature.
Humpbacks under direct observation from Tory Channel lookout hill have been noted as retarded or accelerated by tidal streams in Cook Strait to such an extent that the lookout is often abandoned well before dusk on days in which the afternoon tide sets against the course of the north-bound humpbacks. Thus, although it is certain that there is no consistent relationship between ocean currents and the major movements of humpbacks, the possibility that some of the smaller deviations from certain regions of the coast are locally modified by currents and tidal streams must be considered.
The direction of flow and physical properties of New Zealand coastal waters depend primarily on the relative extent and intermixing of two main water masses—the cool west wind drift of the Southern Ocean and the warm East Australian Current (Barlow 1938, Dell 1952). A boundary of mixed water (the sub-tropical convergence) occurs along the New Zealand coast and differs in position between the west and east coast and also changes in latitude at various seasons (M.O. 516 charts 1949, Garner 1953, 1954). This should make it possible to note the local effects on migration, if any, as the humpbacks cross from cool to warmer waters and encounter a change in direction of current flow at differing points for the two coasts during both the northward and southward migrations.
Humpbacks approaching New Zealand from the south travel in the Southern Ocean drift which, during May to August, flows north-eastwards along the east coast of the South Island as far as Cook Strait. Up to this area the whales therefore move in the same general direction as the drift. Along the east coast of the North Island the current comes as a tongue from the East Australian Current which, on striking the west coast of New Zealand, flows northwards to Cape Reinga, where part of it comes down the east coast of the North Island and is therefore flowing against the general direction of whales migrating up this coast. At East Cape, where the whales could follow an unobstructed route northwards and at the same time be travelling with current partly side on, a large proportion of the local stock turn to follow the coastline and so remain orientated directly against the current. On the other hand those which pass through Cook Strait to travel up the west coast of the North Island are then travelling in the same direction as the East Australian current.
Up the west coast of the South Island the whales first meet a southward deflection of the East Australian Current which appears to fork into streams flowing in opposite directions (Garner 1954) from the Milford Sound Jacksons Bay region. Up to this region the whales are therefore moving against the current, but they then leave the coastline at just the region where the north flowing coastal fork originates. North-bound humpbacks therefore travel both with and against the main current drifts in differing proportions on the two sides of New Zealand, and there is no indication that the direction of current flow modifies the route of north-bound humpbacks.
During October-December south-bound humpbacks along the east coast of the North Island move in the same direction as the current when they follow the coastline to East Cape. South of East Cape they no longer follow the coastline closely, but probably continue temporarily in the same direction as the southward moving tongue of warm water from the East Australian Current. Russell (1950) and Garner (1954) have shown that this current varies in its southward extension, but at the above months it usually extends considerably further south than in the May-August period. By February, in 1951, there was evidence from temperature records
(Garner 1953) that this current continued southwards as a tongue of warm water a few miles offshore almost to the southern end of the South Island.
Close to shore and out beyond the eastern margin of this tongue the water was markedly colder, and Captain Turnbull, of the Port Waikato, which travels between Lyttelton and Chatham Islands, states that he sees whales only when crossing the warm tongue which is frequently partly enveloped by fog. To date this is the only local observation indicating any preference for particular water masses by humpbacks, and it may be purely fortuitous as the tongue extends south along much the same line that southbound humpbacks from East Cape would probably follow in any case.
Along the west coast of the North and South Islands as far as the Jacksons Bay area, humpbacks travel against the current, which also has an arm extending into the southern side of Cook Strait (N.Z. Pilot) and should therefore facilitate the passage of south-bound whales through the Strait. Instead, most of the humpbacks avoid the Strait, and current movements appear to give no solution to this behaviour. Garner (1953) found evidence of an inflow of sub-tropical water from the East Cape current coming into eastern Cook Strait during October. 1950, but this fact does not further an explanation for the humpbacks' route.
South of Jacksons Bay a tongue of the warm East Australian Current is deflected southwards towards Foveaux Strait, and it is along this stretch that the greatest concentrations of south-bound humpbacks accumulate. However, some of this current probably flows through Foveaux Strait as it has tidal streams of up to 3 knots, but Bary (1951) found that Foveaux Strait contained very few oceanic plankton organisms and suggested that the water exchange was not very effective and may be primarily oscillations of an almost stationary body of water. If this proves to be the case it may help to show reasons for the striking turn of the migrating humpbacks from west to south at Centre Island. Nevertheless it is clear from other parts of the New Zealand coast that even in the local movements of humpbacks the nature and direction of flow of the major water masses show no consistent relationship with the known changes of course in New Zealand waters.
The only effect so far recognised has been the retardation or acceleration of humpbacks encountering strong tidal streams, and there has been no evidence of deviations from course which could be attributed to direction or temperature of ocean currents.
After heavy rain has produced a large run-off of muddy water which is often distinguishable as a discoloured zone in coastal waters, especially near river mouths, humpbacks travel further offshore to skirt the turbid area. From the whaling lookout at the entrance to Tory Channel it is sometimes possible to observe humpbacks travelling around the edge of muddy water and even following the projections and indentations closely without entering any tongues of muddy water. The degree of avoidance under these somewhat extreme conditions is too slight for it to be likely that river outflows or coastal turbidity along exposed coasts is an important factor in affecting the migration routes. It does not appear to be related to the main deflections away from the coast, such as the way that north-bound humpbacks leave the coast from Jacksons Bay and Cape Egmont, but it may be a factor in the avoidance of Foveaux Strait. The average depth of the latter is only about 15–20 fathoms, and the Waiau, Jacobs, Oreti and Mataura rivers discharge into it from the South Island, and Patersons Inlet carries sediment from Stewart Island. Foveaux Strait is described by local observers as being frequently muddy, and it may be sufficiently turbid to account for the spectacular change of course in the migrating stocks that approach Centre Island.
(4) Depth of Water.
Many fishermen, especially in the Bay of Plenty to North Auckland area, have commented that they usually sighted humpbacks over waters of 20 to 60 fathoms, and have attached some special significance to these depths. However, there is a range in depth from several hundred fathoms along the south-west corner of the South Island to 20 or less in Bay of Plenty at points approximately the same distance from land, and both are traversed frequently by migrating humpbacks. At Tory Channel humpbacks occasionally enter the channel and have been known to go up as far as Picton, a distance of about 20 miles from the open sea; while Whangamumu whalers have described humpbacks coming in close enough to shore to rub themselves against the rocks in waters of 3–5 fathoms. The net whaling there was carried out for 20 years across a channel only 5 fathoms deep. Apparently even a considerable distance of shallow water is no deterrent to humpbacks, as there is a distance of some 30 miles or more in places of water less than 6 fathoms deep in the approaches to the Carnavon station of West Australia, yet the catches in these shallow waters are excellent. No part of the New Zealand coast avoided by humpbacks is less than this depth, and most are considerably deeper, so it is highly improbable that the depth of water can account for any part of the migration route in this area.
(5) Presence of Whale Feed.
During the northwards migration most of the humpbacks caught at Tory Channel or Whangamumu have had empty stomachs, and the whales are only rarely seen feeding along the New Zealand coast during winter months. There are no records of blooming by Munida gregaria at this season, but the whalers have described swarms of a small, transparent crustacean known to them as mana. On the occasions on which humpbacks have been seen feeding at this time of year, they have been moving through these swarms, and the crustacean remains in stomach contents have been identified by Dr. B. M. Bary as predominantly the euphausid Nyctiphanes australis which has been found compacted into masses of several bushels with the texture of moist chaff. Humpbacks which have been found with crustacea in the stomach were killed during May and the first half of June, and after that time it is exceptional to find food remains in the stomach or the intestine. During the northwards migration there has been no evidence of humpbacks deviating from course to follow possible food concentrations.
The return migration past the New Zealand coast coincides with the earliest swarms of Munida gregaria which occur in large concentrations from Cook Strait southwards between October and February, Young (1925), Marine Department Annual Reports (1928–1935), and from fishermen's descriptions it seems probable that it occurs along the eastern coast of the North Island at the same time of year. Whales have frequently been observed passing through concentrations of red crustacea along the North Auckland and Bay of Plenty coasts, and they appeared to be feeding en route. The swarms of crustacea vary considerably in their distribution per season and during each season, but local observers claim that south-bound humpbacks as well as various petrels follow the concentrations as they appear. For example, humpbacks penetrate much more deeply into the upper reaches of Hauraki Gulf when feed is present there than at other times, and in various areas small groups may remain in approximately the same place for a number of days as though feeding. Most observations of this kind have been made between North and East Capes, probably because south-bound humpbacks are seen much less frequently south of this area. Many of the humpbacks caught near Whangamumu during October to December contained large amounts of crustacea. After December most of the humpbacks are to the south of New Zealand, but the apparent peak of Munida swarming, at least along the east coast of the South Island, occurs between December and
February. Along the latter coast very few south-bound humpbacks are seen, as they appear to travel further offshore than when north-bound, and it is possible that they encounter Munida away from the coast, although there is no evidence to suggest that this is the reason for their route away from the east coast of the South Island.
Near Centre Island in November, large numbers of humpbacks were frequently observed feeding in small schools which circled slowly in the western side of Foveaux Strait. The food organisms were usually too far below the surface to be seen clearly, but there were a number of surface patches from which samples could be taken, and the main organism in each during November was the euphausid Nyctiphanes australis. The patches were discontinuous and all those noted had dense flocks of muttonbirds (Puffinus griseus) and prions feeding on the surface where they served as a valuable guide to the location of humpbacks, which were often feeding in the same plankton shoal. All descriptions for several seasons in the Foveaux Strait area, and my own observations agree that the great majority of south-bound humpbacks entering this region occur on the western side of the Strait, and the density of petrels and plankton shoals noted at the surface are much greater in this area than elsewhere in the strait. Dr. B. M. Bary informs me that there is evidence of upwelling and mixing of water in this region resulting in a much higher plankton production than occurs elsewhere in the vicinity. It therefore seems probable that the deviation of southbound humpbacks from Puysegur Point into western Foveaux Strait may be influenced largely by the high plankton production in the latter locality. After an unknown period of feeding they then continue southwards past the western side of Stewart Island.
In New Zealand sub-Antarctic waters there is evidence (Dawbin 1954) that Munida occurs in dense concentrations and is a major item of diet for the local marine vertebrates from November to April, but there have been only a few reports of humpbacks close to the shore of the Auckland or Campbell Islands. The Munida concentrations were not observed directly and it is possible that both they and the humpbacks occur sufficiently far from land to be seldom seen by shore parties and the crews of small craft in the coastal waters.
The localised humpback concentrations reported at months other than those in which the north and south migrations normally occur, were each associated with local concentrations of food organisms. Those off the Waitaki River mouth in March and April were apparently feeding on transparent crustacea (rather than Munida) and those near Whale Island (Bay of Plenty) in late April and early May were feeding on small fish. Both these groups are described more fully in the section on “Irregular Movements”.
In general, concentrations of feed occur infrequently during the period of northward migration by humpbacks and do not appear to play any part in modifying the routes followed at that time. During the period of their southward migration, humpbacks do feed in the waters between North and East Cape as well as in western Foveaux Strait, and at times they deviate towards local concentrations of feed or linger for a period before continuing south. The “out of season” sightings of humpbacks occur at times and places where whale feed is present, suggesting that some humpbacks remain for relatively long periods in such areas and possibly may not continue to Antarctic waters.
Most of the factors discussed above show little consistent relationship to the route followed by humpbacks in New Zealand waters, and some of them—e.g., the direction of current flow, nature of the water mass and depth of water, show no evidence of appreciable effect on the migration route. Strong tidal streams do sometimes retard, accelerate or possibly deviate humpbacks, but such effects are local and temporary. Turbidity of the water when sufficiently marked causes humpbacks to
detour into cleaner water, and there is some evidence that this may be the reason for humpbacks avoiding central Foveaux Strait, but there is no evidence that it accounts for changes in course along any other part of the New Zealand coast. The presence of whalefeed is greatest in New Zealand waters during the summer months, and at that time south-bound humpbacks appear to deviate into such cul-de-sacs as Hauraki Gulf providing feed is present. They sometimes linger in an area for days at a time in these circumstances and there is some evidence that a small number of humpbacks remain in New Zealand waters possibly feeding on Munida or other shoaling organisms instead of completing the southward migration to Antarctic waters. In spite of this there is no evidence that the main southward pathway is determined by the presence or absence of whalefeed.
The main factor modifying the coastal migration route appears to be the orientation of the New Zealand land mass across the humpbacks' migration route, which shows some tendency to be in a north-westerly or south-westerly direction rather than due north and south in New Zealand waters. If these are the true directions followed, then the northward route along the east coast of New Zealand is explicable, including the tendency to follow the coast between East Cape and North Cape, while large sectors of western New Zealand are avoided. Similarly a return approach from the north-west towards the south-east would be modified by the orientation of the land to produce a course similar to that actually found along most of northern and western New Zealand.
The orientation of New Zealand in relation to the humpback migration routes may also be the main factor in producing the apparent increase in numbers as a cumulative effect near shore from south to north along the east coast of New Zealand during the northward migration and from north to south along the west coast during the southward migration. Some groups of humpbacks from the north-bound stocks which move up the east coast, depart from this stock to go through Cook Strait, and others probably depart from the vicinity of East Cape, so the cumulative effect is partially masked along northern New Zealand. South-bound whales encountering any part of the west coast of New Zealand are deflected to the south-west by the trend of the coastline down as far as Puysegur Point. As very few leave this group to pass through Cook Strait or from any other point until the south-west corner of New Zealand is reached, the aggregations in the latter area probably represent nearly all the humpbacks which encounter any portion of the west coast of New Zealand. These possibly include many of the humpbacks which travelled along the east coast of New Zealand when north-bound, and the great relative size of the aggregation at the south-west corner of New Zealand suggests that it may also include humpbacks which travelled north by some route other than close to the New Zealand coast.
Migration in Oceanic Waters.
While this study has been concerned primarily with an attempt to correlate the finer details of humpback movements with the somewhat varied environmental conditions present in New Zealand coastal waters, it is interesting to consider the implications of the local findings for interpreting the migration route as a whole. It is evident that the movements of humpbacks past New Zealand show much less correlation with local hydrological conditions than Hardy and Gunther (1935) found in the case of blue and fin whales in the Southern Ocean. However, Hardy and Gunther showed that the correlation in the Southern Ocean was probably indirect as the whales were feeding and entering areas rich in Euphausia superba, whose density was intimately related to that of other organisms and phytoplankton, which in turn were dependent on the temperature and quantities of nutrient salts in differing water masses. As little feeding occurs after humpbacks commence migrating to the breeding areas, there is no linkage through a food chain to relate them to particular water masses, and evidence from New Zealand and elsewhere shows that their
direction of movement while on passage has no consistent relationship to hydrological conditions.
In New Zealand coastal waters there is no consistent evidence that migrating humpbacks travel close to shorelines except for those that lie partially across the humpback south to north or north to south migration route. This conclusion receives some support from the nature of the routes followed by humpbacks along the eastern and western shorelines of all the southern continental land masses, but it is clear that deflection by land masses cannot alone account for the distribution of their migratory routes in southern hemisphere waters. The marked concentrations which form along southern continental shore lines can be interpreted in part as accumulations due to the deflection of animals which encounter coastal waters at random points and then move along the coastline to be joined by humpbacks which had encountered the shore line at other points. However, if this were the only major factor modifying the migration routes, then, except for the localised accumulations formed near land masses at the periphery of the oceans, humpbacks would be expected to occur more or less evenly dispersed across the open oceanic waters, but Mackintosh (1942) has already pointed out that few and possibly no humpbacks wander about the open spaces of the Atlantic and Indian Oceans. On the evidence then available Mackintosh included the Pacific Ocean in this category, but it now appears that there are some significant differences between humpback distribution in the latter as compared with the two former water masses, and these differences will be discussed later. Mackintosh also showed that even on the feeding grounds in the Southern Ocean the distribution of humpbacks occurs in segregated groups corresponding to the concentrations known to occur along the major land masses, and he suggested that the distribution of these Antarctic groups are dependent rather on the positions of the southern continents than on hydrological conditions. The present data are in broad agreement with this conclusion, but they do raise questions as to the significance of land masses to migrating humpbacks, seeing there is no evidence in New Zealand latitudes of their following coastlines other than those obstructing their migration course.
In other parts of the South Pacific Ocean, it is now clear from many observations, that humpbacks in substantial numbers pass certain island groups spaced over at least the 3,000 miles between East Australia and the Cook Islands and possibly further to the east. Nevertheless there is no evidence that humpbacks are more evenly distributed over the general oceanic expanse of the South Pacific than occurs in the Indian and South Atlantic Oceans. However, during each seasonal migration period in the South Pacific Ocean, there is evidence of a greater number of humpback aggregations that remain more or less separate from each other throughout the migration, than is known to occur in the South Atlantic and Indian Oceans. Aggregations in the South Pacific, other than those which pass the long coastline of East Australia or the much shorter coastline of New Zealand encounter no long stretch of coastline throughout their migration route.
An hypothesis which appears to be consistent with the available data on humpback distribution is that they require at least some region of coastal waters in the sub-tropical region for breeding, but during other phases of their migration they are not dependent on such conditions except insofar as they encounter them by chance when en route to a suitable breeding area. There appears to be no record of a breeding concentration of humpbacks except in the neighbourhood of some land, either continental or small island groups such as Tonga and other islands in the South Pacific, and the Chesterfield Islands in the Coral Sea. When travelling between island groups in the South Pacific at the time of humpback breeding, the writer has seen few humpbacks away from land but has encountered or been informed of marked concentrations in the coastal waters of several island groups such as Tonga, Niue, Norfolk Island, and the New Hebrides, and has found that this agrees with the experience of many observers in these and other South Pacific areas.
The great majority of observations of breaching, gambolling, striking the water with flippers and other behaviour usually associated with courtship or mating behaviour are made in coastal waters of semi-tropical seas rather than out in the open ocean. It therefore seems probable that humpbacks require some period in coastal waters for normal breeding behaviour. Evidence discussed previously suggests that the period in coastal waters may often be short compared with the duration of the migration to and from the area, or with period spent in the feeding grounds. However, any necessity for humpbacks to congregate in coastal waters would, regardless of the brevity of sojourn, result in the building up of humpback assemblages into the various separated loci which fulfil this requirement. After the formation of such assemblages in tropical coastal waters, the migration routes followed and the relative density of humpbacks in each group would be expected to bear a close relationship to the size and locality of the land masses which served as assembly points.
In the South Atlantic Ocean, for example, islands are so few and isolated that virtually the only regions satisfying the probable requirements for breeding are the continental shore lines of Africa and South America. Therefore even if a hypothetical humpback population were to be distributed evenly across the ocean, it can be assumed that mating and the later calving would occur mainly in those groups near the continental shores, while those in the open ocean would probably not breed to the same extent. Without entering into a discussion of route-finding by whales, there is considerable evidence that individual humpbacks travel in the main to and from the same area each season, so, as the mating and then the calving tended to occur most frequently near coastlines, the calves in their turn would tend to migrate back to such areas. Even a slight tendency this way would result eventually in the whole humpback population achieving the type of distribution now found along the coasts in the South Atlantic.
The presence of numerous islands and island groups in the Pacific Ocean, especially in the western half, provide rather different conditions from the South Atlantic, but the numbers of humpbacks around some of the island groups show that the breeding requirements of many humpbacks are satisfactorily fulfilled in these localities. Mating occurs and calves are born in such areas, and no doubt return in due course to carry on a process which maintains some portion of the humpback stocks in these localities rather than close to a continental coastline. The great length of East Australian coastline situated in the tropics should, however, provide a much more extended area of coastal conditions suitable for breeding humpbacks than is available near Pacific Islands. My observations from East Australia show that many more humpbacks pass close to this coastline than occur near any of the Pacific Islands so far examined. This agrees with the experience of all the mariners and whalers who have examined both localities. Similarly, in the Indian Ocean, the greatest concentrations of humpbacks occur along the coasts of East Africa and Madagascar on the one hand and West Australia on the other. While there are more islands present in the tropical portions of the Indian Ocean as compared with the South Atlantic, they are fewer and much more widely separated than in the South West Pacific, and possibly because of their wide spacing, they do not appear to serve as breeding loci for humpbacks.
In each of the southern oceanic water masses it therefore follows from the nature of the coastal distribution of humpbacks achieved in the tropics that the normal north to south seasonal migration would also result in a segregation into separate areas which would be likely to persist even within the comparatively uniform environment of the Southern Ocean. Mackintosh (1942) has already shown that humpbacks in the Southern Ocean during summer, are segregated into areas which are each related to the coasts of the major southern hemisphere land masses. In the case of Area V, situated to the south of East Australia and New Zealand, it is not yet certain whether all humpbacks from the south-west Pacific intermix each summer or whether there are some small concentrations in Area V and perhaps Area VI to
correspond with the separated breeding aggregations which occur near the island groups.
In northern hemisphere tropical waters the charts of Townsend (1935) show several aggregations of humpbacks some distance from continental shore lines. These aggregations occur near the Lesser Antilles at the eastern margin of the Caribbean Sea, the Cape Verde Islands, and notably the Marianas Is. All could represent concentrations formed by the same process as that described for the South Pacific Ocean.
Where island groups form the breeding area for humpbacks, the stocks whether widely dispersed or in narrow streams during migration, tend to concentrate into the small area of suitable localities during the breeding season, and thus produce several separated accumulations such as occurs in the South Pacific Ocean. Newly born young and the associated adult whales therefore commence in compact but separated groups for their migration to the southern feeding grounds, and may well retain much of their identity as such throughout the migration, until the southern feeding area is reached. Some dispersal appears probable during the months that the animals are actively feeding. At the commencement of the next northward migration it is not improbable that humpbacks commence in a more widely dispersed arrangement than for the southward migration.
The reconstruction outlined in this discussion is consistent with several features of the migration past New Zealand. During the southwards migration two concentrated streams at least have been observed, that off the south-west corner of the South Island and that near the Bounty Islands, whereas north-bound whales are more widely dispersed. The much larger number of humpbacks seen south-bound off the south-west corner of New Zealand than is seen at any other season or locality along the New Zealand coast could result from a process of aggregation of the whales prior to their passage southwards. The shorter period during which southbound whales pass New Zealand, as shown by records both at Whangamumu and Centre Island as compared with the duration of the north-bound passage, is also consistent with their commencement as a more compact group at the beginning of their movement away from the breeding ground. As has already been discussed, the route followed past the New Zealand coast shows little modification by local factors except for the deflections and shadow effects produced by the obstruction of a land mass across a part of the migration route. It is therefore probably determined primarily by factors operating in some other area. This is consistent with the view that the main requirement in the northwards migration is the attainment of some coastal locality whether large or small in area so long as it is situated in tropical waters, and that local factors encountered en route are largely irrelevant to the course followed. From this viewpoint the lack of consistent correlation between humpback migration routes and the direction of ocean currents or other hydrological conditions, bottom topography and proximity of coastline is not particularly surprising.
Certainly the proposition that humpbacks' movements to and from the tropics are primarily the result of a need for coastal conditions in warm waters in order to carry out normal mating and breeding behaviour, is consistent with the known facts of their distribution and segregation into separate groups whether in tropical, Antarctic or intermediate waters, and can be applied equally well to northern hemisphere data. At this stage the writer offers no hypotheses on the nature of the relationship between humpback breeding and their marked preference for coastal conditions at this particular phase of their life cycle. Blue and fin whales which normally do not aggregate in coastal waters during breeding or any other portion of their life cycle remain more widely dispersed than humpbacks in all oceanic areas. The differences between the oceanic distribution during migration of the various species of baleen whale in general may be related to the presence or absence of special requirements at a restricted portion of the migratory cycle. In the case of the humpback it is suggested that an intensive study of environmental conditions and
humpback behaviour in the breeding areas may well prove to be more productive in furthering an understanding of their migratory movements than any similar study of humpbacks on passage or in the feeding grounds.
(1) North-bound humpbacks which travel up the east coast of New Zealand in May to August are first seen in the vicinity of Port Pegasus, Stewart Island, and are seen in small numbers near the Otago coast. Few come close inshore along the Canterbury Bight, but a regular stream passes near the direct line between Otago and Banks Peninsulas. North of Banks Peninsula more are seen near shore, particularly towards Kaikoura, but they deviate out from Cape Campbell before entering Cook Strait, where they pass the site of the present whaling station in Tory Channel. It seems probable that most of the humpbacks which encounter any part of the east coast of the South Island are deflected towards the north-east by the orientation of the coast up to Cook Strait, but on traversing the Strait they are deflected in a north-westerly direction until Cape Egmont is reached. North of this point humpbacks are rarely seen along the west coast of the North Island.
Along the east coast of the North Island other north-bound humpbacks closely follow the coastline in a north-easterly direction as far as East Cape. The only major indentation in this coastline is Hawke Bay, which is largely by-passed by humpbacks. Right whales formerly approached the shore line to the head of the bay, but humpbacks migrate past the entrance of the bay and enter it only at its northern limit on the western side of Mahia Peninsula, which forms a cul-de-sac that necessitates a return to the neighbourhood of Portland Island before the whales are able to resume the north-easterly course. North of East Cape the general trend of the coast-line is towards the west and north-west, and many humpbacks turn to travel in these directions relatively close to the shore line and so pass Whangamumu, which was the site of a well equipped whaling station until 1931. At North Cape many of the north-bound humpbacks depart from the New Zealand coastline, but there is some evidence that a few travel further west towards Cape Reinga before migrating further to the north.
Along the west coast of Stewart Island a further group of humpbacks travel north until they encounter the South Island coast and then travel in a westerly direction along the coastline until Puysegur Point is rounded. From that point many follow the north-easterly trend of the shore as far as Jackson Bay, but they are very rarely seen near the coast north of this region, and it is clear that most of the group leave the coastline to travel in some other direction within the northerly quarter.
(2) South-bound humpbacks encountering the northern tip of New Zealand divide into two main streams, one of which follows the east coast of northern New Zealand, while the other travels offshore from the west coast. Those following the eastern shore line move towards the south-east, and a number enter Hauraki Gulf and the Bay of Plenty paralleling the shore line which runs further east towards East Cape before they resume a southerly course. South of East Cape few humpbacks only are seen near the shore of either the North or South Island which both trend towards the south-east, so it is apparent that their continued migration is in some portion of the southerly quarter on a course which leads away from the coastline. Dense concentrations of south-bound humpbacks observed near Bounty Islands probably represent part of the group which passes East Cape, and if so then the course from East Cape, at least to the Bounty Islands, is almost due south.
Humpbacks travelling along the west coasts follow the general south-easterly trend of the coastline as far as Kawhia Harbour and are then deflected by the shoreline towards Cape Egmont. Instead of then resuming a south-easterly course along the coastline towards Cook Strait, most of the humpbacks travel in a south-westerly direction beyond Cape Egmont on a route which passes parallel to the west coast of the South Island at a distance of 20 to 50 miles or more from the shoreline. The first close approach to the South Island coast occurs in the Jacksons Bay area,
and from this region southwards numerous humpbacks continue travelling close to shore. After rounding Puysegur Point they travel almost due east towards Centre Island at the western approaches of Foveaux Strait, but instead of traversing the Strait they then turn southwards and pass along the western side of Stewart Island before leaving New Zealand coastal waters. Thus, although the western approaches of both Cook and Foveaux Strait are passed by south-bound humpbacks, few humpbacks make the passage through either Strait.
(3) In addition to the two main migrating streams of humpbacks, small groups are observed each year during the summer months at variable points along the east coasts of both North and South Islands, particularly in the Bay of Plenty. These groups are usually observed in the same general area for periods of a week or more and are frequently associated with local blooms of plankton organisms such as Munida or small fish. It therefore seems probable that some humpbacks feed in New Zealand waters rather than continue southwards to the feeding grounds in Antarctic waters.
(4) The season during which the north-bound migration passes through Cook Strait (41° S.) has occurred between the beginning of May and the end of August for at least 36 seasons. The average duration of the passage has been 86 days, while the average commencing and finishing dates have been May 22 and August 16 respectively. During the 36 seasons, dated records for 4,112 humpbacks have been kept and the mid-point—i.e., the date by which half of these had passed to the north of Cook Strait, is July 5. The central half of the humpback group during those seasons traversed Cook Strait in 32 days, while three-quarters of the sightings were recorded in 49 days, showing that the humpbacks are not evenly distributed throughout the migrating group but travel in a relatively compact group on either side of the mid-point and are more widely spaced at the beginning and end of the season. The variability during individual seasons in the number of humpbacks recorded, the duration of passage, the dates between which the north-bound humpbacks pass through Cook Strait and the periods taken for various proportions of the group to traverse the Strait are described and discussed. There are very few records of south-bound humpbacks traversing Cook Strait.
(5) At Whangamumu (35° S.) north-bound humpbacks usually arrive one to two weeks later than in Cook Strati, and were usually recorded through a twelve-week period between the beginning of June and the end of August, while the midpoint for three seasons' records was July 12. South-bound humpbacks for at least 13 seasons passed Whangamumu in approximately equal numbers to those north-bound earlier, and were recorded between late September and early December with the mid-point occurring about October 20. The period of passage past Whangamumu was two or more weeks less than for north-bound humpbacks, showing that southbound humpbacks travel in a more compact group.
(6) At Centre Island (46° S.) north-bound humpbacks are first observed in early May and are seen until mid-August, and show a similar pattern in migration to that past Cook Strait and Whangamumu, but the mid-point of records for four seasons was June 15, and all other dates are correspondingly earlier than at the former localities. South-bound humpbacks are observed between early October and mid-December, with the mid-point for four seasons calculated as November 3. Although approximately seven times as many south-bound as north-bound humpbacks are seen in the area, the south-bound humpbacks pass Centre Island in two to four weeks less time time than do the north-bound humpbacks.
(7) The migration rate of humpbacks passing New Zealand as calculated from the difference in the interval between the peaks of north-bound and south-bound humpbacks at Centre Island, as compared with those at Whangamumu, eleven degrees further north, is approximately 200 nautical miles per week. If this relatively slow rate of overall north or south progression applies throughout the migration period, then the central portion of the stock leaves Antarctic waters in early May,
reaches 46° S. by mid-June, and arrives at the breeding area at latitude 15° S. by mid-August. After a period of approximately six weeks spent in this latitude or in moving to and from some area further north, the humpbacks return towards New Zealand, reaching 46° S. by early November, and arrive at the feeding area about 66° S. by mid- to late December. The beginning and end of the migrating group reach the respective latitudes approximately six to seven weeks earlier or later than the above cycle.
(8) The course followed by the migrating humpbacks, especially in New Zealand waters, shows no consistent relationship to ocean currents and other oceanographic factors or to depth of water and proximity of coastline. There are indications of local and temporary effects from tidal streams, turbidity and presence of whale-feed, but the most important factor appears to be the orientation of the coastline in relation to the direction of the humpback migration.
(9) The details of humpback movements in New Zealand coastal waters, as well as the nature of the course followed in the various oceanic water masses is consistent with the hypothesis that humpbacks require coastal conditions only at the breeding period in sub-tropical waters. During other phases of the migration they are not dependent on coastal conditions except insofar as they encounter them by chance when en route to a suitable breeding area. From this, the migration routes and the differing distribution of the stocks in the various oceans follows as a result of the geographical position of continents and islands, and is little affected by hydrological or environmental factors other than the above.
Many people and organisations have co-operated generously in providing data and other assistance which is acknowledged in the text. In addition, it is a pleasure to record my gratitude to Mr. G. T. Perano, manager of the Tory Channel Whaling Station, for his constant interest and co-operation and for providing much information from diaries and station records. Miss M. Toms, Mr. G. Cook and Mrs. D. Cook kindly loaned logs covering 29 whaling seasons. Valuable sighting data was provided by the Royal New Zealand Navy, Royal New Zealand Air Force, Ministry of Works Aerodromes Branch, and the masters of many trawlers and coastal vessels. From the New Zealand Marine Department a great deal of information was provided by the Principal Keepers of the Lighthouse Service and by Officers of the Fisheries Branch. Whale marking in Hauraki Gulf and Foveaux Strait was supported by the Marine Department, which also financed the publication of this paper. I wish to thank the Secretary of Marine and his officers for such varied assistance throughout a long period. Dr. R. A. Falla kindly supplied records of many observations and gave me the benefit of his comments on a number of points arising from the data. Mr. R. Barwick gave valuable assistance by preparing Figs. 1 and 2. The constructive criticisms and suggestions by Professor L. R. Richardson during this work have been greatly appreciated.
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