Northwest Fisheries Science Center

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Document Type: Chapter or Section
Center: NWFSC
Document ID: 9118
Type of Book: Technical
Section or Chapter Title: Spatial and temporal variability in nearshore forage fish communities in the Strait of Juan de Fuca
Book Title: In-stream flow restoration: making the hydrograph. 2017 Salmon Recovery Conference, 25-27 April 2017, Wenatchee, WA
Author: Anna N. Kagley, Kinsey E. Frick, Kurt L. Fresh, Larry Ward, D. Morrill, J. F. Samhouri
Editor: Greg McLaughlin (Ed.)
Publication Year: 2017
Publisher: Washington State Recreation and Conservation Office, Olympia
Keywords: dam removal, salmonids, forage fish, monitoring,

Forage fish are ecologically and economically important as the foundation of the piscatorial food web, and as the focus of commercial fishing in many locations.  Despite acceptance of these ideas, the population dynamics of forage fish in the Salish Sea are poorly understood.  Over nine years of monthly beach seine sampling (April–September) at 24 sites along 70 km of coastline in the Strait of Juan de Fuca, we have observed high variability in catch across years, sites, and seasons.  Forage fish species dominate net presence, and we have documented the existence of species previously unknown to the region.  The influence of individual species varies, yet can drive the fish assemblage structure and directly impact salmonid populations.  We explored the effects of temporal and spatial variability on forage fish abundance and community composition using a Bayesian hierarchical modeling framework and multivariate analyses.  Three forage fish species dominated our catch and are the focus of additional investigation:  Pacific herring, Pacific sand lance, and surf smelt.  These show species-specific variations across years, seasons, and sampling locations.  Other forage fish species appear to increase when these populations are depressed.  We will expand on the current distributional descriptions through population dynamics analyses for the common forage fish species and determine the effects this may have on local salmonid populations.  Stable isotope analyses will further define forage fish population structure within the Strait of Juan de Fuca and throughout the Salish Sea and allow us to track these species through the food web to salmon and resident killer whales.  This approach may reveal unanticipated risks to the ecosystem that can be mitigated through management revision.

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Theme: Ecosystem approach to improve management of marine resources
Foci: Provide scientific support for the implementation of ecosystem-based management
Describe the interaction between human activities, particularly harvest of marine resources, and ecosystem function.