Variations in the Biological Characteristics of the Patagonian Scallop (Zygochlamys patagonica) Across the Argentine Shelf Break Front

Oceanographic fronts and their associated physical processes create strong spatial patterns of food availability that may influence the metabolic processes of bivalves located within these areas. To investigate this prediction, we used mass size relationships, condition indices, and carbon (C) and nitrogen (N) stable isotopes to evaluate how the biological characteristics of the Patagonian scallop (Zygochlamys paragonica) are influenced by the Shelf Break Front (SBF) and the surrounding chlorophyll a concentration (CSAT). Scallops from 2 transects across the front (38-39 degrees S, 55-56 degrees W, southwest Atlantic Ocean) were sampled with a nonselective dredge in October 2005. The results show that the SBF position, estimated from satellite-derived sea surface temperature, was more stable than the CSAT maximum concentrations. If muscle tissue is considered a better indicator of food shifts as previous studies indicate, scallops located far from the front have lower C isotopic signatures and C/N ratios than scallops located near the front. However, the lack of a shift in scallop organ conditions suggest that spatial differences in food supply are not strong enough during the time of year we sampled to impact scallop development, as may happen at a seasonal scale. Our results show that complicated interactions exist between oceanographic structures, food supply, and scallop life history characteristics.