Effects of Artificial Substrate and Covering on Growth and Survival of Hatchery-Reared Coho Salmon

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Abstract
Coho salmon alevins (Oncorhynchus kisutch) were hatched and incubated in shallow concrete troughs with or without an artificial substrate of plastic netting. Five of 10 troughs with substrate and 5 of 10 control troughs were covered with plywood sheets to block light. After 170 d, the fish were transferred to raceways. At this point, fish that had been incubated on substrate were significantly larger in both mean weight and length than control fish, and they remained so throughout the subsequent 12-month rearing period. During the first 2 months of raceway rearing, mortality of the control groups, particularly the uncovered control, was significantly higher than mortality of the substrate groups. Marine survival rates of the control and substrate groups were equal. The study showed that artificial substrates may not produce coho salmon that are fitter after release from the hatchery but, based on a hatchery production of one million smolts, an expenditure of roughly US$800.00 on substrate can res...