On the by-catch of harbour porpoise (Phocoena phocoena) in German fisheries in the Baltic and the North Sea

The harbour porpoise is the only cetacean known to be incidentally taken by German fishing vessels. This paper reviews data on the by-catch of this species from a reporting scheme based on voluntary compliance by fishermen. More than 95% of the by-catches were taken in set net fisheries. Incidental takes were much better documented for the Western Baltic than for the North Sea. It is not possible to quantify the present level of by-catch, although current evidence suggests that the by-catch level in German fisheries is low both in the North Sea and the Western Baltic. Even though it seems unlikely that the current level of by-catch in the German fisheries alone could exert a significant adverse effect on the stock off the German North Sea coast, those by-catch levels should always be seen in association with by-catches taken in fisheries of other nations and with other impacts on the stock. If harbour porpoise form a separate population in the Western Baltic or are part of the population in the Central Baltic, given the low abundance estimates, even a low by-catch could have a substantial adverse effect on the stock.