106 THE AXGLER AXD HUXTSMAX 



exercised to guard against depleting the natural food. 

 Where there is a shortage in the food supply, the larger 

 trout will prey upon the smaller ones. Owing to their 

 cannibalistic tendency, exceptionally large fish should not 

 be allowed to remain in an inclosure with those of the av- 

 erage size. 



Natural Enemies: 



"Fish inhabiting a pond, especially the smaller ones, are 

 subject to the depredations of numerous enemies. Many 

 kinds of aquatic birds prey upon them, and eggs and 

 young are consumed by snakes and turtles. Among birds, 

 kingfishers, herons, ducks, and fish hawks are the most 

 persistent poachers. Muskrats do not destroy fish, but 

 make burrows in the pond banks. Galvanized-iron wire 

 screens placed in the pond embankments will prevent the 

 burrowing of muskrats. They may be caught with ordinary 

 steel traps. 



Spawning of Trout: 



"Under ordinary conditions neither the rainbow 

 trout nor the brook trout will mature earlier than the 

 third year, although where they have the advantage of good 

 ponds and an adequate and suitable food supply it is not 

 exceptional for them to deposit eggs at the end of their 

 second year. Experience at the hatcheries of the Bureau 

 of Fisheries has shown that from 15 to 25 per cent of the 

 female trout in a pond may be expected to spawn during 

 their second year, 60 per cent in the third year, and from 

 85 to 90 per cent, during each year thereafter up to the 

 seventh, after which it is inadvisable to rely upon them as 

 a source of egg supply. Eggs of the best quality are ob- 

 tained from fish that are from 3 to 5 years old. 



"Two-year old rainbow trout yield from 500 to 800 

 eggs; at 3 years old and thereafter the average is from 

 1,000 to 1,200 per fish. Brook trout yield from 150 to 250 

 eggs at 1 year old, 350 to 600 at 2 years old, and the older 



