Nephrops norvegicus (L.): Comparative biology and fishery in the Mediterranean Sea. Introduction, conclusions and recommendations

Abstract

The project, financed by the Directorate General XIV of the EC, has undertaken a comparative study on the biology and fisheries techniques of the Norway lobster in Mediterranean member states and adjoining Atlantic areas. The ultimate goal of the project has been to assess the conditions for a global regulation in the area and determine possible differences among exploited stocks. The areas selected are characterised by their importance in Norway lobster catch. The overall duration of the project has been three years. Sampling was concentrated in the first two years. Data analysis was conducted during the second and third years (1993-1995). The countries (areas) involved in the study, together with their target areas, were: Portugal (south coast of Algarve), Spain (Alboran and Catalan Seas), Italy (Ligurian, Tyrrhenian and Adriatic Seas) and Greece (Gulf of Euboikos). In order to make results perfectly comparable, each scientific subject has been developed by a specialised team using a unified and standardised methodology. From the biological standpoint, Norway lobster growth, reproduction, moult and feeding have been compared. Special studies on distribution and genetics have been also conducted. In the fisheries context, a comparison of fishing techniques has been undertaken. The fisheries studies have been complemented with reconstruction of virgin populations, comparison of yield per recruit, sensitivity analysis and transition analysis. Selectivity issues have been object of specific analyses. As a result of these studies, it is evident that Norway lobster populations in the Mediterranean follow a common life-cycle model. The differences among areas reported in this project respond to environmental variation and differential fishing pressure in each area. All populations are exploited near its carrying limit, although overexploitation is unlikely at this stage. However we identified varying levels of exploitation according to study areas: The Catalan, Tyrrhenian and Adriatic Seas populations are exploited at a high level; the Ligurian Sea and Euboikos Gulf populations at an intermediate level; and the Alboran Sea and Algarve populations are at a low level of exploitation. The regulation concepts could be applied globally to the Mediterranean, allowing for the differences observed. It is highly recommended that effort is not increased. It should rather be decreased as new technologies being implemented continuously are by themselves an effort increase. A effort reduction of 20% is desirable to ensure that stocks are maintained at their current levels. This measure should be foremost applied to those areas being subjected to the highest exploitation levels.