GoDBY. — Growth of Hroivn T ront in C((iil( rhuni. 



53 



No brown trout have been liberated in Marymere since 1908, and so it is 

 clear that they must breed in the lake itself, as three of the ten fish appear 

 to have been hatched in 1914. It is curious that the next-youngest fish 

 seems to have been hatched in 1911. In dealing with such small samjiles 

 it is dangerous to generalize, but it certainly looks as if 1914 was an excep- 

 tionally favourable breeding season. Plate V, fig. 1, shows a scale from 

 one of these fish hatched in 1914, and Plate V, fig. 2, a scale from one of 

 the older fish. The latter illustrates clearly the difficulty in determining" 

 the age of old fish, owing to the way in which the winter bands are crowded 

 together towards the edge of the scale. It is probable that the per- 

 centage of ova hatched in Marymere, except in very favourable seasons, is 

 abnormally low, and that the stock of fish is maintained mainly by the 

 greater average age attained. Whether this latter is due to natural 

 causes or to the limited amount of angling I am unable to say, but it is a 

 characteristic not only of Marymere but also of other back-country lakes. 

 The average age is 6-4, calcidated to last winter ; and as these fish would 

 probably all have survived until next spawning season their average age 

 would then have been 7-4 years, or about \h vears older than the Selwvn 

 fish. 



Lake Heron. — The average growth is as follows : — 



The full figures are set out in Table IV (B), and the growth-curve is 

 shown in fig. 6 as a continuous line, the Marymere curve being reproduced 



Fig. 6. 



as a broken line for comparison. Although the size of the older fish approxi- 

 mates fairly closely to that in Marymere, the average length of the younger 



