Within-raft variability of the growth rate of mussels, Mytilus galloprovincialis, cultivated in the Rı́a de Arousa (NW Spain)

Abstract

The relative influence of three factors on the growth rate of mussels, Mytilus galloprovincialis, cultivated in an inner area of the Rı́a de Arousa (NW Spain), was analysed. The three factors acted within the raft: position of the culture ropes on the raft, depth of cultivation and stocking density. Results indicate that depth of cultivation is the major factor affecting the growth of the mussels. In the two phases of the cultivation process, from seeding to thinning out and from thinning out to harvest, mussels cultivated in the upper part of the water column (2.5 m depth) were significantly longer and heavier than those in the lower part (7.5 m depth). Effect of the position of the ropes on the raft was less important. Only at harvest, were significant differences in the weight of the mussels detected, with lighter mussels occurring at the back (down-current) of the raft. Surprisingly, stocking density showed no significant effect on the growth of the mussels in any of the two cultivation phases. From the results obtained in this experiment, some recommendations, important for the management of the Galician mussel cultivation, are given.