Past, Present, and Future Shifts in Marine Fish Assemblages in Response to Regional Climate Velocities and Physiographic Constraints

Many studies illustrate shifting species distributions in response to factors like changing temperatures and fishing pressure. Based on four decades of bottom trawl survey data on the U.S. Northeast Shelf (NES), we examine changes in the distribution of four temporally persistent species assemblages, defined by species-specific thermal and bathymetric conditions. Heterogeneous oceanographic and bathymetric features along a northeast-southwest gradient characterize the NES and allow for a comparative analysis of two sub-regions of the shelf, Gulf of Maine versus Georges Bank/Mid-Atlantic Bight, in order to dissect the relative roles of climate and local constraints. Our sub-regional analysis highlights predictable functional relationships and that assemblage responses are related to changes in climate but also strongly dependent on local physiographic constraints and oceanography. Using future bottom and surface temperature projections from high-resolution climate models and assemblage niche models we make longer-term projections of the assemblage distributions and assess the potential impacts of climate change on marine species on the NES under an annual 1% increase in atmospheric CO₂. Our results indicate large-scale changes in the distribution of the biomass on the NES and the need to develop spatial protection strategies to reduce these impacts.