The potential use of environmental information to manage squid stocks

Most commercially exploited squid species have short life cycles and stocks composed of recruits from a single cohort, the size of which is unknown prior to the fishing season. Recent studies suggest that strong environment-recruitment relationships may exist for a number of squid stocks. Using simulation models based on Falkland Island Patagonian squid (Loligo gahi), the recruit abundance of which is predicted by sea-surface temperature, we propose a method for using predictive relationships in the management of squid populations. We compare a management strategy based on recruitment prediction with historical data from the fishery, which was managed in the absence of these predictions. Our results suggest that varying effort on the basis of an environmental correlate of recruitment can reduce the risk of not meeting conservation targets while increasing yield. Effort has to be reduced in years of low abundance but licensing additional effort in years of high abundance increases long-term average catches. Even if effort levels were not allowed to vary by more than 50% between years, a management strategy for L. gahi based on prediction would have resulted in higher average catches and a reduced probability of the stock biomass falling below a notional conservation limit.