Flatfish discarding practices in bivalve dredge fishing off the south coast of Portugal (Algarve)

An evaluation of flatfish discards from bivalve dredge fishing on the south coast of Portugal (Algarve) was undertaken through fishing surveys carried out on board a professional dredge fleet. Data collection of the dredge fishery was carried out between November 2000 and February 2002. The data were compared with information gathered from abundance analysis surveys, and analysed independently of the target bivalve species (Chamelea gallina, Donnax trunculus, and Spisula solida). Flatfish and non-flatfish species accounted for 20.1% and 79.9%, respectively, of the by-catch species of the bivalve dredge fishery. Significant differences have been calculated between length composition of flatfish species in the by-catch and in the abundance surveys. This indicates an optimised performance of the bivalve dredge, which catches a small amount of undersized flatfish as by-catch.