Three Decades of Change in Demersal Fish and Water Quality in a Long Island Sound Embayment

Estuaries are impacted by multiple anthropogenic stressors from eutrophication to climate change. Long-term observational datasets allow the determination of trends in estuarine indicators and the prediction of future conditions. Here, a dataset of water quality and demersal fish community composition in a Long Island Sound embayment (Norwalk Harbor, Connecticut) from 1987 to 2016 was examined. Mean water column water temperature increased, dissolved oxygen decreased, and salinity increased over the study period, with simultaneous changes in the demersal fish community. Fish abundance declined overall, with declines in CPUE observed across multiple species including the commercially important winter flounder (Pseudopleuronectes americanus). As fish can serve as effective indicators of estuarine health, these changes suggest a negative shift in the health of this Long Island Sound embayment. Climate change presents an increasing threat to estuaries and the ecosystem services they provide, especially when coupled with other anthropogenic stressors. Management actions are needed at multiple spatial scales, from local to global, to combat these threats to estuarine health.