Foraging Behavior of Hatchery-Produced Coho Salmon (Oncorhynchus kisutch) Smolts on Live Prey

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Abstract
We presented three groups of naive hatchery-produced, pellet-reared coho salmon (Oncorhynchus kisutch) with live, natural prey and observed their foraging behavior. Of 26 individuals examined, 20 captured one or more Crangon (sand shrimp) within 1 h of their first exposure to these prey. Six older (.gtoreq. 210 mm TL) accelerated smolts (underyearlings) displayed improved foraging performances with experience, capturing their first Crangon sooner during their second, compared with their first, exposure. Four of five of these fish successfully captured sand lance (Ammodytes hexapterus) within 1 h of their first presentation. Two groups of 10 recently smolted fingerlings (< 190 mm TL), one accelerated and one conventionally reared (yearlings), were used in choice experiments and simultaneously offered equal masses of Crangon and pellets. Six of the accelerated and seven of the conventionally reared fish ate larger amounts of Crangon than pellets, with all 20 fish striking more at Crangon than at pellets. Our results suggest that a majority of hatchery-produced coho salmon smolts readily recognize, capture, and ingest natural prey and seem capable of foraging successfully upon release into the marine environment.