Bivalve fishing and maerl-bed conservation in France and the UK?retrospect and prospect

Abstract

1. Maerl beds are carbonate sediments, built by a surface layer of slow-growing coralline algae, forming structurally fragile habitats. 2. They are of international conservation significance, often supporting a high biodiversity and abundant bivalve molluscs. 3. Experimental fishing for scallops (Pecten maximus) on French and UK grounds has shown that although large epifauna are often killed, many organisms escape harm as they burrow deeply or are small enough to pass through the dredges. 4. Bivalve dredging is currently one of the main threats to European maerl grounds as it reduces their biodiversity and structural complexity and can lead to long-term degradation of the habitat. 5. Protecting maerl grounds is of importance for fisheries since they provide structurally complex feeding areas for juvenile fish (e.g. Atlantic cod - Gadus morhua) and reserves of commercial brood stock (e.g. Ensis spp., P. maximus and Venus verrucosa). 6. We outline improved mechanisms to conserve these ancient and unique biogenic habitats.