54 



Transactions. 



fish is distinctly lower, especially at two, three, and four years old. It is 

 also noticeable that the curve is nearly a straight line for the first four 

 years, and that even in the fifth year the falling-oft' is not very pronounced. 

 In dealing with the Sel'wyn fish I pointed out that a curve of this character 

 was to be associated with a sample of fish containing individuals which 

 probably migrated to more favourable conditions at varying ages. An 

 examination of the figures in Table IV (B) shows the characteristic increase 

 of growth to have taken place in every case, and examples can be found 

 of one-, two-, three-, and four-year-old migrants. Lake Heron differs from 

 Marymere in that there are several small tributary streams flowing in and 

 one fair-sized stream flowing out of it. In the spawning season these are 

 packed with spawning trout. No doubt also a large number of trout spawn 

 in the lake itself. I have selected five fish from the fifteen which appeared 

 to have scales similar in character to the Marymere fish, and calculated the 

 average rate of growth as follows : — 



Fig. 7 shows the growth-curve for these, and the broken line shows the 

 growth-curve for the Marymere fish. There is a difference of 1 in. at three 

 years and 0-8 in. at four years old ; elsewhere they agree to within 0-5 in. 



Fig. 



In dealing with such small samples the agreement is most remarkable, and 

 suggests the probability that these fish were bred in the lake itself or 

 migrated as fry. 



