212 U. S. BUREAU OF FISHERIES. 



pose oi holding them during the feeding period, prevented the general 

 adoption of th(^ rearing system. 



For some years certain fish cultm'ists and others had contended that 

 the planting of fry ]ust after they had absorbed the umbilical sac was 

 an economic mistake, claiming that at this age they were weak and 

 comparatively sluggish in their movements, and would fall easy prey 

 to their numerous fish, bird, and other enemies. The late Robert D. 

 Hume, who built and operated a hatchery on the lower Rogue River, 

 also one on the upper Rogue River, which the United States Bureau 

 of Fisheries operated for some years, was one of the first to take up 

 the rc^aring of salmon fry on any scale. 



In time these objections bore weight, and a few years a^o the con- 

 struction of ponds in which fry could b(^ held and fed until they had 

 reached a size which would insure them at least an even chance for 

 their lives was undertaken all along the coast except in British 

 Columbia, with the result that to-day there is a pona capacity for 

 about one-half of the total capacity of the various hatcheries. 



Most of the nursery ponds have been constructed near the hatch- 

 eries and usually comprise oblong trenches dug in the earth and walled 

 with cement and stone. 



In Oregon the State authorities foimd that the best results in pond 

 rearing were obtained by using creek or natural ponds, which were 

 made by placing dams across the small streams in the vicinit}^ of the 

 hatcheries. When first taken from the hatching troughs the fry are 

 placed in the artificial ponds until the danger from spring freshets in 

 the small streams is over. They are then transferred to the natural 

 ponds, where the continual flow of fresh water, and the logs, rocks, 

 etc., which provide shade and shelter, afl'ord more natural conditions, 

 and in which the natural food of the fry supplements the artificial 

 food provided by man. 



A big advantage in connection with the use of natural ponds is the 

 comparativel}^ small expense involved in providing for them as com- 

 pared with the large expense involved in the construction of cement 

 ponds. 



The young fry show when they are ready to feed by dar ing to one 



side or the other when small particles of food are dropped in the water 



and float past them. For the first few weeks they should bo fed 



regularly and as often as six times a day, and the earlier in the day 



the feeding begins and the later it continues at night the better. 



Two hours after feeding they will be found to be ravenously hungry, 



and as they grow much faster for frequent feeding great care should 



be taken to see that they are well fed. If not fed sufficiently they 



will bite at one another and cause more or less mortality among 



themselves. 



FOOD. 



In feeding salmon fry almost every conceivable food has been 

 utilized. By universal consent liver is conceded to be the best food 

 for the fry, as it can be ground finer than other foods and the blood 

 which it contains is highly nutritious. At many places, however, it 

 is impossible to secure liver, while its cost when available is generally 

 prohibitive. 



The food used is generally that most available and which experi- 

 ence has shown that the fry hkc and upon which they thrive. 



