Social and Private Benefits and Costs of Selectivity in the Fishing Industry : a Simple Bioeconomic Model

So-called « technical measures », aimed at increasing selectivity in the fishing industry, are expected to provide several social benefits. However, selectivity also generates costs: direct private cash costs such as gear cost but mainly costs based on the fact that selectivity usually decreases the short-run catch per unit of effort (CPUE) concerning marketable individuals of commercial species. This consideration raises a trade-off between short-run and long-run impacts of technical measures, which depends, inter alia, on the time discount rate. Another trade-off is due to the fact that the long-run net social benefits provided by selectivity depend on the level of fishing effort. Finally, fisheries management has to consider the fact that, due to mutual negative externalities generated by the common-pool character of fish resources, cost-benefit analysis of selectivity measures is not the same at the individual level and at the collective level. In this paper, we develop a bioeconomic model aimed at analyzing these various aspects of the selectivity problem. The model, which is a simplified version of a bioeconomic model of the French Nephrops fishery of the Bay of Biscay, allows computing the short-run and long-run social and private benefits and costs of increasing selectivity for a given level of effort. It also makes it possible to determine the optimal policy-mix between effort and selectivity controls. Finally, it is used for simulating the potential impact of increasing selectivity in a context of poorly controlled effort, a scenario which may be considered as realistic in several circumstances.