Size selection of Nephrops norvegicus (L.) in commercial creel fishery in the Mediterranean Sea

摘要

In the Mediterranean Sea Nephrops (Nephrops norvegicus) is predominantly caught with bottom trawls, but it is also harvested with creels. While the size selection of Nephrops in bottom trawls is well documented, there is no previous information on creel size selection for this species. Therefore, sea trials were carried out to assess the selective properties of commercial creels with 41 mm mesh size netting mounted as a square mesh netting as prescribed by the legislation. Creel size selection was assessed for Nephrops and two main crustacean bycatch species: mantis shrimp (Squilla mantis) and blue-leg swimming crab (Liocarcinus depurator). The influence of the soak time on creel selectivity was also investigated, and no significant difference was detected between one and two day soak times. The average carapace length of a crustacean with 50% probability of being retained (L50) was 31.69 mm for Nephrops, which is 59% larger than the minimum landing size (MLS) set by the fishery regulation, therefore demonstrating a mismatch between MLS and gear selectivity in this fishery. Comparison of creel selectivity obtained in our study with the historical results obtained from commercial bottom trawl selectivity studies for Nephrops in the Mediterranean Sea demonstrated that the creel L50 was significantly higher than in the trawl fishery, this implies that creel fishery is targeting larger Nephrops than trawl fishery.