Abstract
BackgroundHatchery-induced selection and direct effects of the culture environment can both cause captively bred fish populations to survive at low rates and behave unnaturally in the wild. New approaches to fish rearing in conservation hatcheries seek to reduce hatchery-induced selection, maintain genetic resources, and improve the survival of released fish.Methodology/Principal FindingsThis study used acoustic telemetry to compare three years of early marine survival estimates for two wild steelhead populations to survival of two populations raised at two different conservation hatcheries located within the Hood Canal watershed. Steelhead smolts from one conservation hatchery survived with probabilities similar to the two wild populations (freshwater: 95.8–96.9%, early marine: 10.0–15.9%), while smolts from the other conservation hatchery exhibited reduced freshwater and early marine survival (freshwater: 50.2–58.7%, early marine: 2.6–5.1%). Freshwater and marine travel rates did not differ significantly between wild and hatchery individuals from the same stock, though hatchery smolts did display reduced migration ranges within Hood Canal. Between-hatchery differences in rearing density and vessel geometry likely affected survival and behavior after release and contributed to greater variation between hatcheries than between wild populations.Conclusions/SignificanceOur results suggest that hatchery-reared smolts can achieve early marine survival rates similar to wild smolt survival rates, and that migration performance of hatchery-reared steelhead can vary substantially depending on the environmental conditions and practices employed during captivity.
Highlights
Wild and captively-reared salmonids exhibit differences in survival rates [1,2], behavior [3,4], morphology [5,6], and physiology [7,8]
Conclusions/Significance: Our results suggest that hatchery-reared smolts can achieve early marine survival rates similar to wild smolt survival rates, and that migration performance of hatchery-reared steelhead can vary substantially depending on the environmental conditions and practices employed during captivity
Wild smolt survival probabilities from marine entry through the last detection array (RM-Juan de Fuca (JDF)) ranged from 10.0–15.9% for 2008–2010 outmigrants, which were substantially lower than the estimates for wild Hood Canal smolts in 2006 (28.6–41.7%; [21]) and lower than estimates of wild smolts migrating longer distances through the Georgia Basin in 2004– 2006 (18–45%; [29])
Summary
Wild and captively-reared salmonids exhibit differences in survival rates [1,2], behavior [3,4], morphology [5,6], and physiology [7,8]. Some differences, including reduced fitness in at least one hatchery steelhead population [9], reflect effects of domestication selection resulting from adaptation to hatchery environments [10]. Traditional US Pacific Northwest salmon and steelhead hatchery programs for harvest augmentation and mitigation commonly use non-local broodstock and maintain genetically isolated hatchery stocks by intentionally restricting geneflow from wild populations [12]. Hatchery-induced selection and direct effects of the culture environment can both cause captively bred fish populations to survive at low rates and behave unnaturally in the wild. New approaches to fish rearing in conservation hatcheries seek to reduce hatchery-induced selection, maintain genetic resources, and improve the survival of released fish
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