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Marine Ecology Progress Series

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MEPS 515:187-202 (2014)  -  DOI: https://doi.org/10.3354/meps10963

Evidence for selective mortality in marine environments: the role of fish migration size, timing, and production type

Andrew M. Claiborne1,*, Jessica A. Miller2, Laurie A. Weitkamp3, David J. Teel4, Robert L. Emmett5

1Washington Department of Fish and Wildlife, 600 Capitol Way North, Olympia, Washington 98501, USA
2Oregon State University, 2030 SE Marine Science Drive, Newport, Oregon 97365, USA
3Conservation Biology, Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration,
2032 SE OSU Drive, Newport, Oregon 97365, USA
4Conservation Biology, Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration,
7305 Beach Dr. East, Port Orchard, Washington 98366, USA
5Fish Ecology, Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, 520 Heceta Place, Hammond, Oregon 97121, USA
*Corresponding author:

ABSTRACT: The underlying causes of mortality during critical life stages of fish are not well understood, nor is it clear if these causes are similar for naturally versus artificially propagated (i.e. hatchery) individuals. To assess the importance of selective mortality related to production type (hatchery vs. naturally produced) and size at and timing of marine entry, we compared attributes of juvenile Chinook salmon Oncorhynchus tshawytscha from the upper Columbia River summer- and fall-run genetic stock group captured in the Columbia River estuary with back-calculated attributes of survivors captured in marine waters. We used genetic stock identification, otolith chemistry and structure, and physical tags to determine stock of origin, size at and timing of marine entry, and production type. Fish emigrated from fresh water in May to September and the majority of fish collected in the estuary (87%) had arrived within 3 d of capture. In 1 of 2 yr, timing of marine entry for both production types differed between the estuary and ocean: the ocean catch included a greater proportion of juveniles that emigrated in late July than the estuary catch. There was no evidence of selective mortality of smaller juveniles during early marine residence in hatchery or natural juveniles, but the mean percentage (±SE) of hatchery fish in ocean collections was 16 ± 5.8% less than in the estuary, which could indicate reduced survival compared to naturally produced fish. Results from this study highlight the need to understand the effects of hatchery rearing and how hatchery propagation may influence survival during later critical life‑history transitions.


KEY WORDS: Chinook salmon · Early marine survival · Hatchery · Naturally propagated · Size‑selective mortality · Otolith


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Cite this article as: Claiborne AM, Miller JA, Weitkamp LA, Teel DJ, Emmett RL (2014) Evidence for selective mortality in marine environments: the role of fish migration size, timing, and production type. Mar Ecol Prog Ser 515:187-202. https://doi.org/10.3354/meps10963

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