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Volume 79, 1951
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New Zealand Existence

In 1906 fifty thousand eggs of this fish were imported by the New Zealand Government and hatched by the North Canterbury Acclimatisation Society at its hatchery in Christchurch. The Society's Annual Report for 1907 states that 4,000 young fish were liberated in Lake Pearson in Canterbury and a similar quantity was forwarded to Westland for disposal by Government officials. The late T. E. Donne (1927), Government Tourist Officer, at whose instigation the eggs were obtained, gives the Westland locality as Lake Ianthe and states that the Canterbury lot was divided between Lake Pearson and Lake Grasmere. A few of the young fish were retained in the acclimatisation ponds and apparently reared to maturity. The Society's Annual Report for 1910 states that 56 four-year-old fish were held at that time, and it is obvious that a second generation was bred from them, as the 1911 Report records the presence of two-year-olds. There is no account of what became of these fish, but they appear to have been disposed of by 1913, as the only salmonoids recorded as being held in ponds at that time were brown trout and rainbow trout.

The only New Zealand water from which this char has been recorded is Lake Pearson, which is situated about four miles south of Cass, on the West Coast road. This lake has an altitude of 1990 feet and appears to have been ponded partly by moraine and partly by shingle fans. It is about two miles in length and about half a mile in width except at the middle, where it narrows to a neck about 30 yards wide. The principal tributary is the Craigieburn Creek, which is so unstable in the lower part of its course that it may divide its waters between the lake and the outlet stream or flow wholly into one or the other. The Ribbonwood Creek is usually dry in the lower part of its course, but assists in feeding the lake by soakage and there are several small trickles which usually maintain a connected flow. The outlet known as Winding Creek is at the south end and flows into Broken River, a tributary of the Waimakariri, but is frequently dry for a considerable distance just below the lake.

No records of the number of char taken at Lake Pearson have been kept, but it would appear from information received from several anglers who regularly fish the water that twelve fish per year would be a reasonable estimate. The largest fish observed by the writer was 7 lb. in weight and the average for the eight specimens examined is 5 lb. These weights are much lower than those recorded in North America, where fish of 15 lb. and 20 lb. are not rare, and individuals of double these weights are taken occasionally. The small size of the New Zealand fish appears to be explainable on the grounds of unsuitability of habitat, and it is even matter for surprise that the species has established itself in a lake so different from its native waters. The great depths and extremely cold waters of the Canadian lakes, in which this fish abounds, are in sharp contrast to the conditions at Lake Pearson, which is comparatively shallow and warm. A series of soundings showed that a considerable area of the northern section is between 35 feet and 40 feet deep, with a maximum depth of 45 feet recorded about the middle transversely and somewhat south of the middle longitudinally. The neck is shallow and the greater part of the

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southern section ranges from 22 feet to 32 feet in depth. At the time these soundings were taken (March 25, 1950) the surface temperature taken in shade at mid-day was 58°F., while the readings at 35 feet and 45 feet were 56·5° and 55·5° respectively. Seasonal temperatures have not been taken apart from a surface reading of 63°F. obtained on November 29, 1949. These records agree fairly closely with those of better known alpine lakes and suggest that surface readings approaching 70°F. would be obtained in mid-summer.

The growth rate of these char is much more difficult to determine than that of trout on account of the scales being smaller and the ridges more closely placed. This close placing is customary in stunted fish, the scales of which manifest little differentiation between summer zones and winter bands. In the majority of the specimens available the scales are too indefinite to justify even an approximate reading, but after examining a large number of scales of the most favourable specimen the opinion was formed that the fish was in its fifth year. This fish was 23 inches in length and the lengths attained at what appeared to be the completions of the several years were computed as 2·75 inches. 7·5 inches. 15·5 inches and 21 inches. These figures appear reasonable, but in the absence of more definite knowledge of the life history of the species they cannot be accepted unreservedly.

The condition factor of the specimens available, as obtained from Corbet's calculator. averaged 44·6, which would be quite good for trout in similar waters.

The time of spawning cannot be estimated with any precision, as the specimens available were taken early in the season. In a male measuring 24·25 inches in length, taken on November 1, the milt lobes were about 9 inches in length and 0·6 of an inch in width, and in a female of 23·25 inches, taken at the same time, the egg lobes measured 5 inches and contained eggs of up to 2 mm. in diameter.

Particulars of the stomach contents of the eight specimens examined are given in the following table. One stomach was empty.

Stomach Contents of Eight Specimens of Cristivomer namaycush from Lake Pearson
Philypnodon breviceps Galaxias lynx Larvae of Procordulia Sundry
44 1 3 Small quantity of vegetable matter
23 4 2 1 water-snail
38 14 1 beetle, 4 small stones
1 6
26 2
63 7 1 larva of Zantagrion, 1 caddis larva, water-weed and rushes

Compared with the food of trout from Lake Pearson and similar waters the food listed above reveals a marked scarcity of surface insects and a preponderance of Philypnodon. Green manuka beetles (Pyronota festiva) and adult dragonflies of several species form an important part of the food of both rainbow trout and brown trout in alpine lakes, the remainder consisting largely of Procordulia larvae, caddis larvae, water-snails and sundry beetles, with fishes occupying only a minor position.

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Fig. 1—Cristivomer namaycush. Lake Pearson, Canterbury.
Fig. 2—Vomer of Salvelinus fontinalis.
Fig. 3—Vomer of Cristivomer namaycush.

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Several specimens contained the cysted parasite Eustrongylides, one natural host of which (Phalacrocorax carbo) is moderately plentiful in the locality.