Assessing productivity regime shifts in Flemish Cap main stocks

Estimation of fish productivity is a key issue to understand the recruitment process, and hence stock-recruitment relationship, a cornerstone in fisheries management. Several life history traits are involved in productivity and most of these are highly influenced by environmental factors, extrinsic biological factors and fisheries. Strong fluctuations in external factors and internal life history traits may trigger more drastic and consistent changes, i.e. regime shifts. The occurrence of a regime shift implies the existence of different stable states, under which stock performance change dramatically. Stocks with eroded resilience are more prone to modify its performance under changing environment due to reduced fitness, with important implications in fisheries assessment. This study is based in the Flemish Cap ecosystem (Northwest Atlantic, 3M NAFO division) and in four of its key species: Atlantic Cod and three species of Sebastes spp. This research investigates trends in the productivity of these species during the last three decades and tries to disentangle the mixed effects of fisheries, environment and extrinsic biological factors in their life history traits. Unraveling the factors causing changes in productivity provides a better understanding of the current state of these exploited species in order to adapt to a more appropriate management of the stocks.