A comparative study of the species composition of discards from five fisheries from the Algarve (southern Portugal)

Discards from five of the most important fisheries (crustacean trawling, fish trawling, demersal purse seining, pelagic purse seining and trammel netting) in southern Portugal were studied and compared. A total of 236 species of all taxa were discarded, with fish and cephalopods accounting for more than 90% of the discarded biomass, except trammel nets (81%). Although there was some overlapping of species, multivariate analysis using cluster analysis for classification and multidimensional scaling (MDS) for ordination, showed that there were significant differences between the five gears in terms of species composition and biomasses discarded, with the least similarity between crustacean trawling and all other fishing operations. The differences between fisheries were probably as a result of a combination of gear selectivity and depth fished. The results suggest that discarding practices are likely to have different, yet significant impacts on the marine ecosystem, warranting further studies on the fate of discards, the factors influencing discarding and mitigation