The impact of marine closed areas on fishing yield under a variety of management strategies and stock depletion levels

Closing areas to fishing has been mooted as an approach to management that hedges against uncertainty. We apply a closed area model to establish the impact of closure on yield, with the explicit inclusion of stock mobility and density dependence. We specifically address two key issues. First we examine how yield is affected by closures under four distinct management strategies. Our purpose is to determine broad scale trends in the dynamics determined by the inter-relationship between management strategy, stock mobility, proportion of habitat closed, yield and stock level, as well as to establish how closures can enhance yield during the recovery of overexploited stocks. Second, we consider how closures can hedge against uncertainty in stock levels and catch and contribute to yield reliability. By quantifying the relative impact on yield of replenishment from closed areas, we provide a means of measuring the impact of closures on overexploited stock recovery times, and we show how closures can prevent overexploitation without reducing yield. Finally, we interpret our results in a manner that informs optimal closure design for a required management outcome. Our analysis suggests that yield does not increase with closure; however, yield decreases only marginally in many cases and there is considerable benefit for fishing reliability through stock protection. Furthermore, our results indicate that stock mobility and management strategy impact on yield and recovery in a fundamental way.