Development of mussel (Mytilus galloprovincialis) seed from two different origins in a semi-enclosed Mediterranean Bay (N.E. Spain)

Growth and mortality of mussel seed from two different Mediterranean ecosystems, a small semi-enclosed bay (Fangar) and an open sea area (Masnou), were investigated in Fangar Bay (Ebro Delta) using standard procedures. Mussel sampling was performed on a monthly basis from October 2002 to August 2003, in conjunction with monitoring of hydrobiological parameters. Environmental parameters varied over a broad range and their fluctuations showed a similar pattern at the three depths studied (0, 1 and 3 m). Seston quantity (total particulate matter, TPM) ranged between 2.7 and 14.95 mg l− 1, whereas the percentage organic matter in the TPM varied between 11.56% (November 2002) and 60.98% (August 2003). Growth results showed that mussels developed from bay seed maintained a greater length than those from open waters from October 2002 to February 2003, but there were no differences in length between both groups from March 2003 until the end of the experiment. Although there was no significant difference in final length for the two seed sources, better performance was observed for bay seed with respect to weight (both shells and soft tissues) and mortality. There was no correlation between the seasonal pattern of mussel growth in Fangar Bay and primary production, temperature or seston, probably due to the wide-ranging variation of these parameters. Seasonal growth patterns were coincident between shell and soft tissues, with the exception of August, when shell weight was maintained and flesh weight diminished. The results of yield in weight and mortality obtained in this study showed the benefits of using mussel seed from the same area where the cultures are carried out.