Survival of Rainbow Trout Sac Fry Subjected to Various Formalin and Hand-Picking Regimes during Rearing in Vertical-Flow Tray Incubators

M.E. Barnes, W.A. Sayler, R.J. Cordes-2002

North American Journal of Aquaculture, 64(2): 129–135

Abstract:

Sac fry of rainbow trout Oncorhynchus mykiss cultured in vertical-flow incubators were subjected to various combinations of physical (hand-picking) and chemical (formalin) antifungal treatments starting at either the eyed stage of egg development or at hatch and continuing until their removal from the incubator trays at fry swim-up. In all experiments, increases in the frequency of hand-picking resulted in increased mortality. The elimination of hand-picking by the use of daily formalin treatments consistently produced the greatest fry survival. Attempts to determine the effect of no fungal control measures were unsuccessful because of excessive fungal growth. To achieve substantial labor reductions and maximize fry survival, we recommend daily formalin treatments of 1,667 mg/L for 15 min throughout the entire residence of salmonid eggs and sac fry in vertical-flow incubators, unless there are overriding human health or environmental concerns.

(South Dakota Department of Game, Fish and Parks, McNenny State Fish Hatchery, 19619 Trout Loop, Spearfish, South Dakota 57783-8905, USA)

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