Torrey and Lance field. — Rearing Salmon 153 



behind those of the same age that had remained in the 

 hatchery troughs in running water. While the yolk sacs 

 of the latter had been absorbed by March 1, the yolk sacs 

 of the former were still prominent when they died, three 

 weeks later. 



The water in the dishes used was 2.5 cm. deep, with a 

 surface 9 cm. in diameter, and a volume of 150 ccm. 

 Under these conditions 30 fish lived for almost three 

 weeks, in a quantity of water equal to 5 ccm. per fish. 

 With 30 to 50 ccm. per fish, the latter lived much longer ; 

 but their rate of growth was materially retarded in cor- 

 relation with a diminished rate of absorption of the yolk 

 sac — that is, a diminution in food supply. 



The volume of water per fish is thus seen to be a factor 

 in development. It is also true that the amount of sur- 

 face exposed to the air per unit of volume, or the shape of 

 the body of water, exerts a definite influence upon the 

 result. Five fish in an open bottle filled to the neck with 

 55 ccm. of water with a surface 1 cm. in diameter died 

 over night, January 7-8. In troughs where the water is 

 being renewed several times an hour, we have compared 

 the rate of growth of fishes in water at depths varying 

 from 7 to 14 cm., but have found no significant difference 

 in the rate of their growth. 



