| Nearshore distribution and residency of pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta) fry and their predators in Auke Bay and Gastineau Channel, southeast Alaska - :12471 | National Marine Fisheries Service (NMFS)
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Nearshore distribution and residency of pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta) fry and their predators in Auke Bay and Gastineau Channel, southeast Alaska
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    A total of 23,785 pink salmon (Oncorhynchus gorbuscha) and 51,462 chum salmon (O. keta) fry were sampled from mid-April to mid-June 1991 by beach seining at 12 sites in the nearshore estuarine waters of Auke Bay and Gastineau Channel, Southeast Alaska. Salmon fry dispersed rapidly from Gastineau Channel, but aggregated and reared more extensively in Auke Bay. The CPUE of salmon fry was higher in Auke Bay than Gastineau Channel. Pink salmon fry fork lengths were greater in Auke Bay than Gastineau Channel Higher zooplankton abundance, higher water temperature, and slower currents in Auke Bay than in Gastineau Channel may have contributed to the larger pink salmon fry and higher abundance of pink and chum salmon fry in Auke Bay. The recovery pattern of tagged chum salmon indicated that fish from the early May releases from Gastineau Hatchery and Sheep Creek Hatchery in Gastineau Channel migrated north over the Mendenhall River bar to reach Auke Bay. More tagged chum salmon fry were recovered in Auke Bay (133) than in Gastineau Channel (14); no tagged pink salmon was recovered in either location. Salmon fry from the late May releases did not use the nearshore environment as extensively as fry from early May releases, which suggests that later release timing of hatchery fish may minimize the potential for density-dependent interactions with fry from wild stocks in littoral habitats. Predators of salmon fry totaled 854 coho salmon (O. kisutch) smolts, 769 chinook salmon (0. tshawytscha) smolts, 368 great sculpins (Myoxocepahlus spp.) and Pacific staghorn sculpins (Leptocottus armatus), and 320 Dolly Varden (Salvelinus malma). Although chinook salmon smolts were equally distributed in Auke Bay and Gastineau Channel, the CPUE of coho salmon smolts, great sculpins, and staghorn sculpins was higher in Auke Bay. The CPUE of Dolly Varden was higher in Auke Bay than Gastineau Channel during peak salmon fry abundance in nearshore waters in May. Thus, in their migration from Gastineau Channel to the more productive waters of Auke Bay, salmon fry also moved from an area of low predation pressure to an area of higher predation pressure. In addition, the movement of fry from Gastineau Channel across the narrow, shallow Mendenhall River bar may have increased fry exposure to predation by birds and fish, before fry reached Auke Bay

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