Temporal and small-scale spatial variation in spatfall of the mussel Mytilus edulis platensis: Basis for culture management at San Jorge Gulf, Patagonia Argentina

Abstract

Despite the commercial potential of mussel populations along the Patagonian coast of Argentina, studies on mussel farming and fisheries to the south of parallel 42° S are clearly insufficient thus far. In this study, variations in mussel settlement (between sites and across depths) were monitored for 12 months at two contrasting sites in San Jorge Gulf, Argentina. The effect of depth on spat density was evaluated through monthly samples taken from artificial collectors at three depths (3, 7 and 11 m). The temporal settlement pattern was consistent at both sites, with the maximum spatfall recorded in early March (late summer), coinciding with the peak of sea water temperature. Settlement also correlated with Chl a and particulate organic carbon peak values, typically manifesting 2–3 months later and followed the initial decline in mussel condition during late spring and early summer. Significant differences between localities were detected in settlement abundance. The optimal temporal gap for mussel settlement was observed in mid / late summer, suggesting that this is the optimal time to deploy spat collectors in the field. Settlement was uniform between depths, thereby implying that the specific depth of collector placement did not appear to emerge as a key factor of settlement success.