When Do Trout and Grayling Fry Begin to Take Food?

Abstract

opinion among fish-culturists as to the time when trout and grayling fry should receive their initial feeding. The most common practice is to offer food when the fry first swim up, i.e., at the time when the fish have absorbed sufficient yolk to enable them to rise from the bottom of the hatchery trough and remain up in the water, at least for a limited time. Henshall (1904, 1907) fed trout and grayling fry before the yolk sac was entirely absorbed. Leach (1923a) reports that brook trout begin to feed as soon as the yolk sac diminished sufficiently to allow the fish to rise and that grayling fry (1923b) began a search for food about one week after hatching. He indicates that rainbow fry should receive food at the time when the umbilical sac is absorbed. Steuert (1901) found that brown trout first ingested food 31 days after hatching and that by the 35th day almost 100% of the fish were feeding. The interesting experiments of Atkins (1905) showed a greater mortality in brook trout fed early than in those deprived of food for five days. Fasting beyond the fifth day increased the rate of mortality in brook and lake trout but not in silver salmon. He questions the practice of very early feeding even though the fry are capable of taking food. Some experiments designed to secure definite information on the time of ini-