Patterns and Drivers of the Demersal Fish Community in Chesapeake Bay

Continued efforts in developing and implementing ecosystem based fisheries management rely on comprehensive understanding of fish community structure and dynamics.  Large-scale research on the environmental drivers of fish distributions, abundances, and community structure can not only identify patterns and trends within systems, but also help provide mechanistic insight into ecosystem functioning.  This study synthesizes 10 years of fishery independent bottom trawl data to evaluate drivers of the demersal community structure in Chesapeake Bay, the largest estuary in the U.S.  Aggregate community metrics (species richness and indices of total fish biomass) are modeled using generalized additive models and changes in community composition are assessed using constrained correspondence analysis.  The models evaluate the relative influences of physical factors, climatic drivers, biological factors, and fishery landings in explaining community patterns.  The demersal community experienced shifting patterns in species dominance resulting from decreasing biomass of Atlantic croaker in the system despite high estimates of recruitment.  Both species richness and biomass indices exhibited strong nonlinear relationships with salinity, positive relationships with temperature, and greatly depressed values in hypoxic areas.  The factors structuring the community are evaluated and discussed relative to spatiotemporal scales and prevailing hypotheses on the mechanisms influencing fish production in the Bay.