Spatial pattern,harvesting and management of the artisanal fishery for purple clam (Amiantis purpurata) in Patagonia (Argentina)

The purple clam Amiantis purpurata supports a small-scale fishery in Patagonia by two modalities: (i) hand gathering along the beach (intertidal zone); (ii) diving fishery in the subtidal zone. In the first case, the influence of the fishermen's behavior (serial depletion of patches, degree of organization, economic threshold) on the catch per unit effort (CPUE) was analyzed. Harvesting processes in subtidal portions of populations were described matching the spatial distribution of abundance, derived from pre- and post-harvest surveys (1995 and 2005), and from temporal patterns of CPUE. Concentration profiles were used to establish an economic threshold; only 16.4% of the clams were dispersed in unprofitable areas. Reduction of density is in accordance with absence of recruitment during two decades. A management scheme was proposed with operative short-term management actions and strategic long-term components to avoid recruitment overfishing.