GROWTH OF MUSSELS (MYTILUS-EDULIS GALLOPROVINCIALIS) ON CULTIVATION RAFTS - INFLUENCE OF SEED SOURCE, CULTIVATION SITE AND PHYTOPLANKTON AVAILABILITY

Mussel seed, obtained from the intertidal zone; and permanently immers ed collector ropes, was cultivated on ropes suspended from three rafts located at three different sites within the Ria de Arousa (Galicia, N W Spain), Sites were characterized by different levels of phytoplankto n availability. The source of seed stock had a marked influence upon s ubsequent mussel growth; seed originating from collector ropes had hig her growth rates than seed collected from intertidal areas and was pro bably due to the higher condition index and previous adaptation to rop e culture conditions (permanent immersion) for these samples. Cultivat ion site also affected mussel growth; differences in chlorophyll a con tent and water current speed, which influence phytoplankton availabilt y, were the major factors underlying variation in growth rate and cond ition index. It is recommended that seed obtained from collector ropes should be used in the commercial exploitation of this species, since it would shorten the total duration of the cultivation process by more than 10%.