Changes in spawning-stock structure and recruitment pattern of red mullet, Mullus barbatus, after a trawl ban in the Gulf of Castellammare (central Mediterranean Sea)

The increase in biomass of red mullet, Mullus barbatus, in the Gulf of Castellammare (northwestern Sicily, central Mediterranean) after a 14-year trawl ban, prompted us to compare the spawning-stock structure and the recruitment pattern before and after the closure. Datasets obtained from three experimental trawl surveys were available before the ban (April and September 1985; April-May 1986) and four post-ban (September and November 2004; March and May 2005). Spawning-stock biomass increased significantly after the ban. Moreover, females at depths .50 m in the post-ban period were larger than those collected before the ban at the same depth. The recruitment pattern of the population also changed. Notably, recruit numbers increased and recruitment occurs over a broader period. The increase in biomass after the trawl ban seems to be the result of a combination of different processes, mainly associated with the lowering of fishing mortality. A positive trend in sea surface temperature in the area may have played a role too.