Stochastic bioeconomic modelling of alternative management measures for anchovy in the Mediterranean Sea

Maravelias, C. D., Hillary, R., Haralabous, J., and Tsitsika, E. V. 2010. Stochastic bioeconomic modelling of alternative management measures for anchovy in the Mediterranean Sea. - ICES Journal of Marine Science, 67: 1291-1300.The purse-seine fishery for anchovy in the Aegean Sea consists of two main fleet segments (12-24 and 24-40 m vessels); this paper investigates economically and biologically preferable effort and capacity scenarios for the fishery. Attention is paid to a bioeconomic analysis of fleets composed of segments with varying levels of efficiency (in terms of catch rate) and costs (fixed and variable) and the role this might play in optimal effort allocation at a fleet level. An age-structured stochastic bioeconomic operating model for Aegean anchovy (Engraulis encrasicolus) is constructed. It attempts to account robustly for the multiple uncertainties in the system, including (i) the effort-fishing mortality relationship, (ii) the selectivity, and (iii) the stock-recruit dynamics of the population. A method is proposed for determining the economically optimal level of long-term effort in a fishery such as this, with similar characteristics in terms of stock dynamics, fishery, and markets. Lower values of effort and capacity are predicted to yield greater future profit when viewing the fleet in its entirety, but even lower values may be advisable to maintain the long-term biological integrity of the stock. The results may prove useful in balancing the productivity of the stock with the harvesting capacity of the fleet, while managing to ensure the long-term profitability of the fleet along with the sustainability of the resource.