SETTLEMENT OF MUSSELS MYTILUS-GALLOPROVINCIALIS ON AN EXPOSED ROCKY SHORE IN RIA-DE-VIGO, NW SPAIN

The mussel farming industry of the Galician region (NW Spain) requires that 60 to 70% of its seed supply is taken from rocky shore areas. However there are almost no quantitative data for a recruitment and settlement pattern. In the Ria de Vigo a continuous settlement throughout the year with a major settlement season from May to September was found, reflecting the presence of spawning mussels throughout the year and the occurrence of a major spawning period during the spring. The observed settlement pattern indicates the direct settlement of larvae from the plankton onto the adult beds and an immigration of mussels previously settled on other substrates. This pattern could be a response to the ecological and environmental conditions that occurred on the Galician rocky shores, but could also be a differential characteristic between Mytilus edulis and M galloprovincialis.