The effects of fishing effort and environmental variability on fish community dynamics on Georges Bank

Understanding the effects of fishing effort and climate variability is vital for the implementation of Ecosystem Based Fisheries Management.  Georges Bank, a historically important fishing ground, has undergone substantial shifts in community composition under intensive exploitation and environmental variability.  Here, we use biomass estimates of 26 fish species collected during Northeast Fisheries Science Center autumn bottom trawl surveys on Georges Bank from 1963 to 2009 to discern the effects of fishing and environmental variability on the dynamics of the fish community.  We aggregated species into five major functional groups: gadids, flatfish, other groundfish, skates, and small pelagics.  We then explored multivariate autoregressive models using these groups in a state-space framework with incorporation of Atlantic Multidecadal Oscillation (AMO), fishing effort and sea surface temperature anomaly.  Significantly negative interactions among some system components, including flatfish and skates, and flatfish and pelagics were observed, reflecting potential competitive interactions among the former and predator-prey interactions among the latter.  The AMO tended to be significantly negative related to the biomass dynamics for flatfish, other groundfish and skates.  We explore these results from the perspective of fish community compensatory responses to exploitation, reflecting both direct and indirect effects of harvesting under the influence of climate variability.