Selectivite des chaluts en polyamide dans la peche de la langoustine

Net selectivity in fishing the Norway lobster, Nophrops noruegicus (L., 1758), has only until now been the subject of a limited number of publications. Among the authors who have approached the problem, POPE and THOMAS (1965), COLE and SIMPSON (1965), FIGUEIREDO and THOMAS (1967) emphasized the great variability of the results. The research work that we present here does not claim to be exhaustive. It is appropriate, in fact, to emphasize that our data come from a selectivity campaign mainly devoted to hake (DARDIGNAC, HÉDÉ-HAUY and PORTIER, 1968). The trawls that were used on board the Thalassa are very different, as much by their design and their dimensions as by their meshing, from those used on board the small fishing ships that hunt Dublin bay prawn in the Gulf of Gascony. Furthermore, we concentrated mostly on phenomena relating to the bag, whereas in this type of fishing a large selection occurs in the lower wings and the belly of the trawl, the opposite of what is generally seen for fish (COLE and SIMPSON, 1965). It seemed nonetheless worthwhile to take advantage of the abundant material—in fact, young hake and Dublin bay prawns are both found in large concentrations on the muddy and sandy sea beds where the experiment took place—and to compare the results obtained by different methods during the same campaign. Moreover, we tried to highlight the influence of certain factors on selectivity.