Go to National Library of New Zealand Te Puna Mātauranga o Aotearoa
Volume 63, 1934
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Section VII.—Summary.

(1)

Scale papillae are first observed along the lateral line, slightly posterior to the dorsal fin. From this area they gradually develop in an anterior and posterior direction along the lateral line, at the same time spreading dorsally and ventrally, until eventually the whole surface of the body is covered. They tend to spread more rapidly dorsally than ventrally.
(2)

The average length of the young fish when scales first make their appearance is approximately 3.5 cm.
(3)

The scales from different regions of the body in the case of the brown trout (Salmo trutta) vary considerably in anterior-posterior diameter, and the number of circuli occurring along the anterior radius. This variation is not entirely due to casual variations in the scale, but is caused by definite local differences, which may to a certain degree be correlated with the time of scale formation in the young fish.
(4)

The number of circuli laid down in any one scale increases from the head to the adipose fin, and then decreases to the tail.
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(5)

A similar distributional variation is shown to occur in the length of the posterior and anterior radius of the scales.
(6)

The average number of circuli laid down in each scale, anterior to the dorsal fin, is greater above than below the lateral line, but posteriorly, and slightly beyond the adipose fin, the reverse is indicated—namely, the ventral scales possess on an average a greater number of circuli.
(7)

The nature of the winter bands, and the time of year during which they are formed, varies in different individual fish taken from the same locality.
(8)

The bands of narrow circuli may begin to form as early as February, or, on the other hand, summer growth (broad circuli) may persist until April. The majority, however, show the beginnings of a winter band on their scales by March.
(9)

The bands of narrow circuli, seen on the scales of brown trout in New Zealand, are laid down generally during the autumn and winter months of the year, while bands of relatively broad circuli are formed during the spring and summer months.
(10)

Early in September the summer band begins to develop, and by the end of October the majority show summer growth to be taking place.
(11)

There is a definite correlation between the growth of the fish and the growth of the scales.
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