Historical and recent patterns of marine biodiversity in the Gulf of Maine and Georges Bank

Developing historical baselines for marine biodiversity conservation is problematic due to the difficulty in linking past with more recent patterns. Currently, biodiversity assessments in the Gulf of Maine and Georges Bank rely heavily on National Marine Fisheries Service (NMFS) bottom-trawl surveys that monitor commercially valuable groundfish. Ecological community metrics provide tools for comparative study to bridge patterns of historical marine communities with more recent ones. Through a statistical analysis, NMFS bottom-trawl surveys (1963-2007) are compared to observations from 19^th-century, fisheries-independent surveys by the U.S. Commission of Fish and Fisheries vessel Fishhawk (1880-1899). The study area includes the western portion of the Gulf of Maine and Georges Bank and the northern section of the Mid-Atlantic Bight. Genera and fish species richness, and guild composition were compared over space and time. Fishhawk trawl surveys detected more genera in the late 19^th century than in NMFS bottom-trawl surveys; however, NMFS bottom-trawl surveys detected more fish species. The guild composition was similar for both surveys with respect to demersal species but not pelagic. These differences in richness and composition may be best explained by changes in gear technology and complexity of bottom habitat.