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Impacts of diving ducks on herring populations

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Herring productivity in relation biomass (Francis et al.).

Puget Sound Institute Lead Ecologist Tessa Francis attended the 2015 meeting of the International Congress for Conservation Biology earlier this month in Montpellier, France. She presented results from her recent work with colleagues at NOAA’s Northwest Fisheries Science Center evaluating the impacts on Puget Sound herring populations of herring egg predation by seabirds and other predators.

The group is evaluating the causes of local declines in herring subpopulations, or “stocklets,” and suspect that heavy egg predation by diving ducks, especially scoters, may be preventing some herring populations that are already at low levels from recovering. Using a combination of in situ incubations and predation exclusion devices, Francis and her colleagues estimated that predation accounted for between 75 and 99.6% of egg mortality in several Puget Sound stocklets, including the sharply declining Cherry Point herring stocklet. They further found that high egg mortality rates are associated with stocklets that have been declining in recent years or decades.

Pacific herring are a foundational species in Puget Sound, owing to their critical position in the marine foodweb, and the Puget Sound Partnership has set recovery targets for herring. These results suggest that an assessment of the impacts of early life stage mortality on population trends, and prospects for recovery, warrants further investigation.