File:Tuohy et al. 2018 chum non-natal habitat use.pdf

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Tuohy_et_al._2018_chum_non-natal_habitat_use.pdf(file size: 3.87 MB, MIME type: application/pdf)

Tuohy, A., Wait, M., Healy, J. F., and A. Jorgenson. 2018. 2018 Hood Canal Juvenile Chum Salmon Nearshore Habitat Use Assessment. Prepared for U.S. Navy. Wild Fish Conservancy Northwest.



Habitat protection and restoration are vital to the survival and recovery of many salmonid populations in the U.S Pacific Northwest. However, conservation actions that fail to consider specific behaviors and life-history strategies demonstrated by a species or population of concern are unlikely to achieve recovery objectives. Building upon a two-year genetic study in Hood Canal, WA that developed statistical models to retrospectively assign chum salmon (Oncorhynchus keta) catch to genetically distinct summer and fall population groups, the non-profit Wild Fish Conservancy performed a nearshore study within Hood Canal to determine habitat preferences by chum salmon population group. Results of the study suggest that summer and fall chum salmon fry exhibit differential use of nearshore estuarine habitats within the Hood Canal that may be dependent on seasonal nearshore ecosystem conditions. Previous research has determined that cooler and less productive estuarine emergence conditions cause early emerging chum salmon juveniles—most of which are now known to be of summer run origin—to emigrate at a faster rate from Hood Canal than later emerging fall chum salmon. Differences in nearshore ecosystem conditions and subsequent impacts on emigration likely result in reduced summer chum residence time within seasonally unproductive delta habitats. This may be the cause of the relative increase in winter season use of barrier lagoon and estuary habitats observed within the Hood Canal outmigration corridor and the significantly lower probabilities of chum salmon occurrence in delta habitats in comparison to later spring months. These findings demonstrate the importance of embayment habitat features (such as barrier lagoons and estuaries) to the recovery of Endangered Species Act (ESA)-listed Hood Canal summer chum salmon. Protection and restoration of embayment features will help maintain or increase shelter and feeding opportunities for juvenile chum and Chinook salmon that may seek substitute rearing habitats to seasonally unproductive or anthropogenically diminished river deltas prior to entering the North Pacific Ocean.

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