Discards of the beach seine fishery in the central coast of Portugal

Abstract

The beach seine fishery is performed regularly along the Portuguese coast in shallow water sandy areas. The catches and discards of this fishery were studied from March until November 1999, on the coast south of Lisbon. Fishing operations were monitored weekly and estimates of the weight of catches and discards per species were determined for each haul. A total of 60 fish species was identified in the catches but Scomber japonicus, Trachurus trachurus and Diplodus bellottii represented approximately 90% of the catches. For most of the species the percentage of discarded fish was extremely high (ca. 100%). The species for which the estimates of discards were lower than 25% of the catches were Sardina pilchardus, Merluccius merluccius, Dicentrarchus labrax, Dicentrarchus punctatus, T. trachurus, several Sparidae species, Spicara maena, S. japonicus, Solea senegalensis, and Solea solea. Most of the species exhibited a marked seasonal abundance pattern that varied according to the species. Discards also varied considerably within and between seasons. The relationships between discards and total catch, species catch, mean length of fish and percentage of fish above minimum legal size were different according to species. For S. japonicus and S. pilchardus discards were negatively correlated with their catch, mean length of fish and percentage of fish above minimum legal size, while for T. trachurus significant correlations were obtained only for the last two variables.