30 FISH CULTURE. 



certain flow for hatching, and perhaps a cold brook which 

 he can also use in supplying his ponds. He will therefore 

 wish to know the size his ponds should be, and the best 

 form. Before I give any directions on incubation and its 

 appliances I will treat of ponds, remarking by the way, 

 that if one uses brook water to increase his supply, he 

 should not introduce it, if avoidable, into his first pond 

 where the small fry are kept, and should make some con- 

 trivance for shutting off the brook or confining it to its usual 

 volume in time of heavy rains. He should do this, not 

 only that he may keep the water in the first pond at its 

 usual temperature, but also to prevent dirt from being 

 washed in, which will soon foul the bottom with mud. 



The plan usually pursued with those who raise trout as a 

 " crop," is to have a series of ponds connected by race- 

 ways, the latter being used as spawning-grounds for the 

 fish. At least three ponds are required. The first for the 

 young fish from the time they are taken from the hatching- 

 trough or nursery, until they attain the age of eighteen or 

 twenty months. The second pond for the same brood for 

 the next twelve months, at the end of which time they will 

 be thirty or thirty-two months old. The third pond for the 

 same fish from the age last mentioned, until they are three 

 years and a half old. From the last pond it is supposed 

 they are to be taken for sale or the proprietor's table. It 

 will be observed, that when the last pond is vacated the 

 trout from the second pond will occupy it, that the second 

 will be occupied by the fish from th first, and the first pond 

 by the new brood from the nursery. 



