Oyster mortality in Delaware Bay: Impacts and recovery from Hurricane Irene and Tropical Storm Lee

•Extreme storms Irene/Lee in 2011 generated unusually low salinity in Delaware Bay.•Upbay oyster beds experienced continuous low salinity (<7) for more than 20 days.•This prolonged low salinity led to higher than normal oyster mortality (10–55%).•Ecological model projections indicate biological impacts will last ∼10 years.

One predicted consequence of climate change is increasing variability of local weather extremes such as the frequency and intensity of storms. In August and September of 2011, Hurricane Irene and Tropical Storm Lee generated extreme flooding in the Delaware River watershed that produced prolonged baywide low salinity and consequent historically-high mortalities for the oyster stock in the upper reaches of Delaware Bay. The dynamics, consequences, and projections for recovery from the anomalously high oyster mortality that occurred as a consequence are reported using a combination of physical modeling, field sampling, and metapopulation dynamics modeling. Monthly mortality of 10% and 55% on the upper bay beds (Arnolds and Hope Creek respectively) exceeded the longer-term average at those locations and was associated with a continuous low salinity (<7) exposure of greater than 20 days. Population recovery projections based on metapopulation modeling suggests that recovery will take approximately 10 years for the uppermost beds. Clear understanding of the circumstances leading to this high population-level impact on oysters is important because anticipated future conditions of increased storm frequency will intensify the challenge such events pose for the management of fishery and aquaculture resources, and the siting of restoration efforts.

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