ARTIFICIAL PROPAGATION OF TROUT. 27 



CARE OF THE FRY. 



"With the approach of the hatching period great care must be 

 taken to guard against the clogging of outlet screens by accumu- 

 lations of eggshells. As the eggs hatch the fry drop through the 

 trays to the bottom of the trougTis and remain there during the sac 

 stage, which varies in length from 25 days in water with a tempera- 

 ture of 50° to 50 days in a water temperature of 33° to 35°. As the 

 young fish develop they will show a tendency to congregate near 

 the head of the trough. To guard against suffocation of the fry, the 

 troughs should be subdivided into compartments by the insertion 

 of screens. The use of baskets for the retention of the fry also 

 obviates this difficulty. 



PLANTING THE FRY. 



"VYlien the weight of the yolk sac has diminished sufficiently to 

 permit the fish to rise in the water, they begin taking food, and 

 under normal conditions are feeding freely by the time the sac has 

 entirely disappeared. When very young fry are transferred to 

 open waters, where there is natural food only, the planting should 

 be done 8 or 10 days before the sac is entirely absorbed, for if 

 delayed till after the sac disappears many will die before they 

 become accustomed to finding food in their new environment. Very 

 good results may be expected from the planting of fry if they are 

 properly handled and carefully deposited in small spring-fed 

 tributaries not frequented by larger fish. 



Brook-trout fry are usually transported in ordinary round-shoul- 

 dered milk cans of 10 gallons' capacity, the number of fish per can 

 dejjending entirely upon the temperature of the water in which 

 they have been held, the distance they are to be carried, and the 

 facilities for taking care of them en route, such as opportunities 

 for changing the water, supplying fresh ice, etc. From the fact that 

 water absorbs air more rapidly at a low temperature it can readily 

 be seen that more fish can be transported per can when the water 

 is cold. However, trout may not be subjected to great and sudden 

 changes with safety, and it is not wise to lower the temperature in 

 the transportation cans more than 10° below that of the water in 

 which they have been carried in the hatchery. In making trips 

 of from 5 to 10 hours' duration between 2,500 and 3,000 fry may be 

 carried in each can if the temperature of the water is not above 

 50°, but where they are to be on the road more than one day it is not 

 safe to carry more than 1,500 per can. 



The distribution work of the Bureau of Fisheries is accomplished 

 mainly by means of cars especially built for the purpose and 

 equipped with pumps for forcing air currents through the cans in 

 which the fish are carried. Small shipments, however, are made by 

 a special messenger in a baggage car, the railway companies usually 

 offering every available opportunity for securing fresh supplies of 

 water and ice. In the case of public plants, the fish upon arrival at 

 the railway point nearest their destination are transported to the 

 stream where they are to be planted and liberated in small lots in 

 different places where there is shallow water and a good bottom or 



