Demersal Fishes of the Thames River Estuary, Connecticut: Decadal-Scale Trends in Relative Abundance and Species Diversity

The Thames River, Connecticut, is a salt wedge estuary located on Long Island Sound. It supports a diverse assemblage of commercially and recreationally important species and is subject to a variety of human impacts. To study long-term shifts in the fish community concurrent with environmental change in the region, undergraduate students (cadets) at the U.S. Coast Guard Academy and their instructors have been collecting beach seining and bottom trawl data on a weekly basis from late August to early October for >20 years, starting in 1974. Field methods have been remarkably consistent over time, yielding a valuable long-term data set unique to the region. In this study, we focus on observed trends in demersal finfish biodiversity and relative abundance across four decades: 1970s, 1990s, 2000s, and 2010s. Preliminary results indicate that species richness and diversity decreased by more than 50% from the 1970s to 1990s and fluctuated after that.  The relative abundance of species has changed over time, from winter flounder (Pseudopleuronectes americanus), dominant in the 1970s and 1990s, to scup (Stenotomus crysops) in the 2000s and 2010s.  Understanding the fluctuation of finfishes and possible links to climatic and other environmental variability is important for the management of fisheries.