Lack of trophic competition among wild and hatchery juvenile chum salmon during early marine residence in Taku Inlet, Southeast Alaska
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Abstract Early marine trophic interactions of wild and hatchery chum salmon (Oncorhynchus keta) were examined as a potential cause for the decline in harvests of adult wild chum salmon in Taku Inlet, Southeast Alaska. In 2004 and 2005, outmigrating juvenile chum salmon were sampled in nearshore habitats of the inlet (spring) and in epipelagic habitat at Icy Strait (summer) as they approached the Gulf of Alaska. Fish were frozen for energy density determination or preserved for diet analyses, and hatchery stocks were identified from the presence of thermal marks on otoliths. We compared feeding intensity, diets, energy density, and size relationships of wild and hatchery stocks (n = 3123) across locations and weeks. Only hatchery fish feeding intensity was negatively correlated with fish abundance. In both years, hatchery chum salmon were initially larger and had greater energy density than wild fish, but lost condition in early weeks after release as they adapted to feeding on wild prey assemblages. Diets differed between the stocks at all inlet locations, but did not differ for hatchery salmon between littoral and neritic habitats in the outer inlet, where the stocks overlapped most. Both diets and energy density converged by late June. Therefore, if density-dependent interactions affect wild chum salmon, these effects must be very rapid because survivors in Icy Strait showed few differences. Our study also demonstrates that hatchery release strategies used near Taku Inlet successfully promote early spatial segregation and prey partitioning, which reduce the probability of competition between wild and hatchery chum salmon stocks.




  • Content Type Journal Article
  • Pages 1-16
  • DOI 10.1007/s10641-011-9899-7
  • Authors
    • Molly V. Sturdevant, Auke Bay Laboratories, Alaska Fisheries Science Center, National Marine Fisheries Service, 17109 Pt. Lena Loop Rd, Juneau, AK 99801, USA
    • Emily Fergusson, Auke Bay Laboratories, Alaska Fisheries Science Center, National Marine Fisheries Service, 17109 Pt. Lena Loop Rd, Juneau, AK 99801, USA
    • Nicola Hillgruber, Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Pt. Lena Loop Rd, Juneau, AK 99801, USA
    • Carl Reese, Alaska Department of Environmental Conservation, 410 Willoughby Avenue, Juneau, AK 99801, USA
    • Joe Orsi, Auke Bay Laboratories, Alaska Fisheries Science Center, National Marine Fisheries Service, 17109 Pt. Lena Loop Rd, Juneau, AK 99801, USA
    • Rick Focht, Douglas Island Pink and Chum, Inc, 2697 Channel Drive, Juneau, AK 99801, USA
    • Alex Wertheimer, Auke Bay Laboratories, Alaska Fisheries Science Center, National Marine Fisheries Service, 17109 Pt. Lena Loop Rd, Juneau, AK 99801, USA
    • Bill Smoker, Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Pt. Lena Loop Rd, Juneau, AK 99801, USA





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