Type of Presentation

Oral

Session Title

Ecological and cultural context of Pacific herring in the Salish Sea

Description

Forage fish such as Pacific herring (Clupea pallasii) are ecological foundation species in marine and estuarine ecosystems. In the Salish Sea, Pacific herring are an indicator species, and the regional management agency, the Puget Sound Partnership, has set recovery targets to guide herring management. Salish Sea herring are spatially and temporally segregated into individual subpopulations by their spawning behavior, and these subpopulations show asynchronous abundance trends over the past several decades. Some local spawning subpopulations have significantly declining trends. Here we focus on the embryonic stage as a potential limiting stage for herring, describing variability in hatch rates across different subpopulations, and assessing the relative importance of predation in determining herring egg hatch success. We then explore the implications of predation rates for observed local trends in herring biomass. Using a combination of in situ incubations and predation exclusion devices, we estimated herring egg survival rates both in the presence and absence of large predators, across multiple spawning subpopulations in the Salish Sea. We found that predation accounted for approximately 50% of egg loss across all spawning populations. We link predation rates to 40+ years of herring biomass estimates for each spawning population and trends in major egg predators (diving ducks) to develop hypotheses about stressors that limit recovery of herring in the Salish Sea.

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The Role of Egg Predation in Pacific Herring Population Dynamics in the Salish Sea

2016SSEC

Forage fish such as Pacific herring (Clupea pallasii) are ecological foundation species in marine and estuarine ecosystems. In the Salish Sea, Pacific herring are an indicator species, and the regional management agency, the Puget Sound Partnership, has set recovery targets to guide herring management. Salish Sea herring are spatially and temporally segregated into individual subpopulations by their spawning behavior, and these subpopulations show asynchronous abundance trends over the past several decades. Some local spawning subpopulations have significantly declining trends. Here we focus on the embryonic stage as a potential limiting stage for herring, describing variability in hatch rates across different subpopulations, and assessing the relative importance of predation in determining herring egg hatch success. We then explore the implications of predation rates for observed local trends in herring biomass. Using a combination of in situ incubations and predation exclusion devices, we estimated herring egg survival rates both in the presence and absence of large predators, across multiple spawning subpopulations in the Salish Sea. We found that predation accounted for approximately 50% of egg loss across all spawning populations. We link predation rates to 40+ years of herring biomass estimates for each spawning population and trends in major egg predators (diving ducks) to develop hypotheses about stressors that limit recovery of herring in the Salish Sea.