Fish and Blue Crab Assemblage Structure in a U.S. Mid Atlantic Coastal Lagoon Complex

Variability in assemblages of organisms in contiguous lagoons is dependent upon component bays and their connections to the ocean and terrestrial watersheds. Fish and blue crab assemblage structure of Maryland’s coastal lagoon complex, which consists of Assawoman, Isle of Wight, Sinepuxent, and Chincoteague Bays, was analyzed for spatial and seasonal patterns for the period 1991–2002. Nonmetric multidimensional scaling ordinated sites from a Maryland state trawl survey into discrete groups associated with each embayment. Dominant species included Callinectes sapidus, Anchoa mitchilli, Leiostomous xanthurus, Bairdiella chrysoura, and Brevoortia tyrannus. The relative abundance of these and other dominant species were significantly higher in the two bays north of the ocean inlet than in bays south of the inlet. Ninety-two species were identified in the survey, with total species richness highest in the southern-most bay (Chincoteague: S 5 83) and lowest in the northern most bay (Assawoman: S 5 59). On a catch per unit effort basis, the northern two bays were more diverse and productive. These bays were most affected by anthropogenic eutrophication, but also exhibited higher connectivity to the ocean inlet. There was clear seasonality in assemblage structure with peak abundance and diversity in the summer compared to spring and fall. Factors that influenced seasonal and spatial structure of Maryland’s coastal lagoon complex included temperature, degree of eutrophication, and proximity to oceanic exchange. The arrangement of the bays in their exposure to oceanic and watershed influences specify that habitat management actions should occur at a bay-level scale rather than across