Contrasting deterministic and probabilistic ranking of catch quotas and spatially and size-regulated fisheries management

Abstract

Large uncertainties over the dynamics of resource systems have increasingly led to the use of probabilistic modeling in the provision of model-based fishery management advice. However, deterministic analysis still remains the easiest and quickest approach to formulate model-based management advice. Here, we contrast deterministic and probabilistic modeling methods in evaluations of the potential consequences of alternative fishery management measures such as spatial and temporal closures and size-specific regulations. We thereby assess how model-based fishery management advice may vary between deterministic and probabilistic analyses of system dynamics. Using data for the sandbar shark (Carcharhinus plumbeus) population off the eastern coast of the USA, it is shown that under a variety of conditions, the use of management measures that provide protection to specific age groups of a population, such as size limits, might be less effective in achieving stock recovery of slow-growing, late-maturing, highly mobile species than catch quotas. It is also shown that management approaches that, according to deterministic calculations, appear to be the most effective are not so when uncertainty in the population dynamics is taken into account.