Observations on gas-bubble disease of fish

SOME DIFFICULTY has been experienced in raising fry and young fingerlings at the Puyallup hatchery of the Washington State Department of Game, a hatchery now in its fourth year of operation. There has been evidence of gas in the yolk-sac fry, and the mortality was always excessive among the fingerlings while reared in the hatchery troughs. The mortality rate decreased and evidence of gas-bubble disease disappeared when the fish mere moved to outside ponds. Also, fish seemed less susceptible to parasitic diseases when held in the ponds rather than 1m hatchery troughs. Strains of fish raised at the station were cutthroat trout (Salmo clarkii clarkii and Salmo clarkii lewisi) rainbow trout (Salmo gairdnerii gairdnerii), and steelhead trout (Salmo gairdnerii iriatus)