Environmental and Anthropogenic Factors Affecting Community Structure within and Among Northwest Atlantic Ecosystems

We used the abundance-occupancy (A-O) relationship in order to quantify temporal trends in the spatial organization of northwest Atlantic demersal communities. This method tracks macro-scale interspecific habitat utilization, making it possible to investigate overriding factors affecting biotic distributions. Using data from the National Marine Fisheries Service’s trawl survey, we estimated abundance in each year as the average number of individuals caught per trawl. Occupancy was then estimated as the number of trawls where a species was present divided by the total number of trawls attempted, making it an indicator of geographic prevalence. We compared patterns within and among four northwest Atlantic regions (i.e. Gulf of Maine, Georges Bank, Southern New England and the Mid-Atlantic Bight) in order to assess spatial similarities in community responses. Lastly, we correlated regional trends to a number of relevant environmental and anthropogenic variables (e.g. temperature, productivity, landings and others). Preliminary results indicate that only in specific regions did community structure vary over time. Where changes did occur, they generally pointed to a decrease in the use of available habitat. This research is relevant to conservation and management efforts as it identifies drivers of large-scale distributional patterns in economically important coastal fishery regions.