^ (lend (wliite) eggs from tray, 

 cell and the darker colored eggs a 



A 



•e al 



.. .. \\y hatclied fry 

 lut to liateh. 



before the water enters the liatch- 

 ery. Silt also may be drawn from 

 the stacks of eggs by raising dam 

 boards between stacks and drawing 

 the water down the entire trongh. 

 This should not be done during the 

 critical development stages when 

 the eggs are green. 



Rearing 



Most hatcheries have a number of 

 ponds in which the young salmon 

 are reared to larger sizes. It is a 

 generally accepted principle that 

 the larger the fish are when released, 

 the better the chance of survival to 

 maturity. Chum and pink salmon 

 fry normally migrate to salt water 

 inmiediately upon emerging from 

 the gravel of the stream bed, so 

 these species are released from the 

 hatchery as fry. Fall chinook 

 salmon fry usually ;tre reared in 



hatchery ponds for a few weeks to 

 several months, the time depending 

 upon the capacity of rearing facili- 

 ties. For the best results with 

 spring chinook, I'ed, and silver 

 salmon, and steelhead trout, the 

 young hsh nuist be reared for a 

 year or more. Silver and spring 

 chinook fingerlings released in the 

 second spring about II/2 years after 

 spawning have produced good re- 

 turns, whereas the release of silvers 

 at small sizes has given unsatisfac- 

 tory returns. 



It is apparent that the rearing of 

 some species of salmon for varying 

 periods is necessary for adequate re- 

 turns. It is equally true that such 

 rearing can be justified on a basis of 

 economics, the hatchery costs being 

 calculated against the returns of 

 adult Hsh to the commercial and 



30 



