A top-down survival mechanism during early marine residency explains coho salmon year-class strength in southeast Alaska |
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| Institution: | 1. Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, B8000ICJ Bahía Blanca, Argentina;2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;3. Instituto Nacional de Investigación y Desarrollo Pesquero, C.C. 175, B7602HSA Mar del Plata, Argentina;1. Department of Geography, Memorial University of Newfoundland, Newfoundland and Labrador, St. John''s, NL A1B 3X9, Canada;2. Department of Geography, University of Victoria, Victoria, BC V8W 3R4, Canada;3. JASCO Applied Sciences, 2305–4464 Markham Street, Victoria, BC V8Z 7X8, Canada;4. Fisheries and Oceans Canada, Aquatic Ecosystems Marine Mammal Science, 4160 Marine Drive, West Vancouver, BC V7V 1N6, Canada;1. Department of Geosciences, Idaho State University, Pocatello ID83209-8072, USA;2. Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China;3. Department of Civil and Environmental Engineering, University of Nevada, Las Vegas NV89054-1087, USA;4. Department of Watershed Sciences, Utah State University, Logan UT84322-5210, USA |
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| Abstract: | Coho salmon (Oncorhynchus kisutch) are a vital component in the southeast Alaska marine ecosystem and are an important regional fishery resource; consequently, understanding mechanisms affecting their year-class strength is necessary from both scientific and management perspectives. We examined correlations among juvenile coho salmon indices, associated biophysical variables, and adult coho salmon harvest data from southeast Alaska over the years 1997–2006. We found no relationship between summer indices of juvenile coho salmon growth, condition, or abundance with subsequent harvest of adult coho salmon in the region. However, using stepwise regression, we found that variation in adult coho salmon harvest was largely explained by indices of juvenile pink salmon (Oncorhynchus gorbuscha) abundance (67%) and zooplankton abundance (24%). To determine if high juvenile pink salmon abundance indicates favorable “bottom-up” lower trophic level environmental conditions for juvenile coho salmon, we plotted abundance of juvenile pink salmon against growth and condition of juvenile coho salmon. No change in growth or condition of juvenile coho salmon was observed in relation to the abundance index for juvenile pink salmon. Therefore, we hypothesize that coho salmon year-class strength in southeast Alaska is influenced by a “top-down” predator control mechanism that results from more abundant juvenile pink salmon, which serve as a predator buffer during early marine residency. |
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