The by-catch situation in German brown shrimp (Crangon crangonL.) fisheries with particular reference to plaice (Pleuronectes platessaL.)

Abstract

Summary Since 1928 and over the history of German fishing for brown shrimp (Crangon crangon L.), several investigations have been made examining the by-catch of this small-meshed fishery. By-catch of commercially valuable fish, particularly flatfish species, has always been a matter of concern. The amount of by-catch comprising fish and invertebrates may actually be high, but figures discussed in public are biased by including discarded undersized shrimp, the target species, and dead material. Many changes in the equipment and practices of the fishery have occurred through the decades. As a result, the overall balance between consumption shrimp, by-catch and undersized shrimp has changed in a positive sense. Those fish still taken as by-catch despite the use of more selective trawls are often discarded and no longer landed for reduction purposes, leaving a chance to survive. Their species spectrum is largely stable over time. In this paper, detailed considerations are made in the particular case of North Sea plaice (Pleuronectes platessa L.), which are abundant in the by-catch and is a commercially important species. Any large numbers discarded must be regarded in the light of high numbers of offspring, the large discards of the flatfish fishery and the high natural mortality of juvenile plaice. From that the conclusion is drawn, that the German shrimp fishery meets criteria of sustainability in respect to the target species and by-catch situation.