Effects of clam rake harvesting on the intertidal Ruditapes habitat of the English Channel

Recreational and professional clam fishing was an important activity on the extensive intertidal zone of the western Cotentin coast (western English Channel). A variety of fishing gear was used to harvest the target species: the European clam Ruditapes decussatus (Linnaeus, 1758) and the introduced Manila clam R. philippinarum (Adams and Reeve, 1850). In this study, we studied the effect of rake harvesting during the spring tides of February-March 2014, following an experimental design with a control station and three stations impacted by rake harvesting in three sediment types: sandy, gravelly, and mixed gravelly rocky habitats. No significant sediment and macrofauna changes occurred at the three sites after rake harvesting. Nevertheless, the number of clams decreased significantly after raking on the gravelly habitat, whereas in the other two habitats, sediment transport in this high-energy hydrodynamic environment was able to transfer clams and other macrofauna species across the fishing sites, thus minimizing the effects of rake harvesting. Therefore, although the effect of rake harvesting appeared limited during winter, the regional impact (high fishing pressure along 60 km of coast) and increase of recreational fishers during summer needed to be studied in the future.