Effects of shrimp fisheries on reefs of Sabellaria spinulosa (Polychaeta)

Abstract

Intensive beam-trawl fishery on brown shrimps (Crangon crangon) occurs along the German North Sea coast. Fishing effort has increased constantly over recent decades. Simultaneously, changes in the benthos of the Wadden Sea have been observed. Besides shifts in species composition of the communities and the disappearance of oyster beds, there has been a distinct decline in the occurrence of Sabellaria reefs. Investigations were carried out to establish whether or not shrimp fisheries might be responsible for the decrease of the reefs. Underwater video techniques enabled direct observation to be made of the fishing gear in action on the sea bottom. The pictures revealed that shrimpers may trawl over the robust reef structures without causing visible damage. These findings are corroborated by the results of field experiments performed on the reefs of Sabellaria alveolata on the French Atlantic coast, and also by empirical calculations of the load of the fishing gear and the compressive strength of the reef. Reasons for the decline of Sabellaria reefs on the German North Sea coast are discussed with respect to natural and anthropogenic changes in the physical environment. © 2000 International Council for the Exploration of the Sea.