MUSSEL (MYTILUS-GALLOPROVINCIALIS LAMARCK) COLONIZATION ON ARTIFICIALSUBSTRATES IN THE RIA DE VIGO OF NW SPAIN

Mussel colonization of available substrates is performed by settlement of competent pediveliger and post-larval stages. To determine the per centage of mussels of each settling type and their relation with cultu re practice, mussel settlement on artificial substrates was studied at different places and depths on mussel rafts from the inner and outer areas of the Ria de Vigo, N W Spain. This was done during the mussel s ettlement season in the area (April to August, 1992). Mussel settlemen t was more abundant on the mussel raft placed in the seaward area (69% of total spat) than in the upper estuary (31% of total spat) of the R ia. Settlement was similar in different places (west side, middle and east side) of a mussel raft, with slightly more recruitment at the 10 and 5 m depths than at the 1 m depth. In the seaward area, 83% of tota l spat settled were competent pediveliger stages, whereas in the upper estuary competent pediveliger stages accounted for only 57% of total spat recruitment. At the start of the season the settlement of compete nt pediveliger stages was almost 100% of the different settled stages, whereas at the end of the season the proportion of competent pediveli ger decreased to 30%.