PISCICULTURE AND NATURAL HISTORY 103 



England so favourably situated in every way to produce 

 such happy results, but where such exist this system is 

 well worthy of trial. 



THE RELATIVE VALUE OF FOOD STUFFS FOR TROUT 



The relative value to trout of the best varieties of the 

 different food stuffs may be roughly estimated as follows. 



If fed on : Increase in weight. 



Water insects in their larval or flying condition . . . . 100% 



Meat 50% 



Fish 38% 



Cereal or bread stuff 12% 



There also appears to be a distinction, attendant on their 

 food, in the habits of the young trout, the insect eaters being, 

 as a rule, more active and better shaped. It seems, 

 however, that the large size to which New Zealand trout 

 attain is largely due to the presence of a very great quantity 

 of small silver-hued fish, locally called Whitebait. 



Some idea of the size of the fish in the Lower Chilland 

 Hatcheries may be gathered from the fact that the two-year- 

 old fish, ready for delivery in January, average nine inches, 

 but that a certain number of two-year-old fish attain twelve 

 inches in length in April of the same year. The fish in the 

 Lower Chilland Hatcheries are largely bred from ova taken 

 from the wild fish of the Itchen. 



Variations in the temperature of the air and water 

 exercise a most important influence on aquatic life. 



The relative increase in the temperature of water assists 

 and quickens the incubation of all sub-aqueous eggs, and 

 hastens the metamorphosis of all insect life. 



Under favourable circumstances the rapid growth of a 

 trout is extraordinary. Trout from the upper waters of the 

 Dart, where natural food is scarce, and the fish in conse- 

 quence are small, quickly grow to a very large size when 



