Establishing the role of the North Atlantic Oscillation as a potential driver of brown crab Cancer pagurus density

Identifying and understanding environmental drivers responsible for fluctuations in stock biomass remains a key knowledge gap in data limited commercial crustacean fisheries such as the brown crab Cancer pagurus. This study investigated the use of historic beam trawl data as a fishery independent density index and its relationship with fishery dependent data. The role of the North Atlantic Oscillation (NAO), a key latent predictor, and other environmental drivers (brooding temperature, larval development temperature and phytoplankton density) on density of C. pagurus in the North West Irish Sea was also investigated. The identification of a significant relationship between fisheries dependent and independent data demonstrates the role of fisheries independent survey data to monitor changes in density in C. pagurus populations. Lagged NAO, brooding temperature and larval temperatures had significant effects on C. pagurus density, with negative NAO phases and increasing brooding and larvaal temperatures resulting in increased C. pagurus density. The significance of these relationships is explored in the context of our understanding of relative stock status and future sustainable fisheries management for C. pagurus in the North East Atlantic.