Shifting species assemblages in the Northeast US Continental Shelf Large Marine Ecosystem

The Northeast US Continental Shelf Large Marine Ecosystem (NES LME) has experienced 2 major pressures: fishing and climate. The magnitude and rate of response to these pressures are species-specific and depend on each individual species' behavior, physiology and life histories. Thus, species assemblages can be expected to change as a result of the sum of each individual species' response. In previous studies, distinct species assemblages have been identified in each of the 4 subregions by which the NES LME has traditionally been assessed: Mid-Atlantic Bight (MAB), Southern New England (SNE), Georges Bank (GB), and Gulf of Maine (GOM). In this study, we confirm that each subregion has a distinct species assemblage, but found that those assemblages are shifting over time. The shift appears to be towards species that prefer warmer water. The result is a species assemblage within each subregion that more closely resembles the historic assemblage found in the adjacent subregion to the south. These shifts have occurred in response to a combination of both fishing and climate, and are highly nonlinear. Therefore, current reductions in fishing pressure may not be adequate to return the system to a more historic species assemblage.