Management and ecology of the wedge clam (Donax trunculus) in the NW Mediterranean Sea: The case of Ebro Delta (NE Spain)

Abstract

The wedge clam (Donax trunculus) is one of the most prized clam species fished in the EU. Clam fisheries have experienced a dramatic decline during the last decades on Spanish coasts resulting in the progressive closure of fishing grounds. The Ebro Delta (NW Mediterranean Sea) is one of the few areas of the Spanish coast where there is still some fishing activity. In this context, the main objectives of this study were: to provide novel data on the ecology of this species and to analyse the management of D. trunculus fisheries in the Ebro Delta. The results showed a depth segregation phenomenon and suggested that D. trunculus performs two migrations during its benthic life cycle, i.e., (1) the settlement of planktonic larvae occurs more intensely in the deepest part of its bathymetric distribution, where the survival was more intense. As clams progressively increase in size, they move to shallower areas; (2) adults tend to move back to the deepest part of their bathymetric distribution as they increase in size. The management of D. trunculus has improved significantly in the last decade. However, some issues are still unsolved (e.g., fishing gear limits are unclear; population boundaries do not coincide with political boundaries). Moreover, the shallower areas where juveniles are located concentrate the highest fishing pressure over the stock.