Population estimates, extraction, and translocation of the pectinid Argopecten purpuratus within Mejillones Bay, Chile

Abstract

The population of the scallop Argopecten purpuratus in Mejillones Bay, Chile (23°S) was estimated using diving-quadrat techniques between July and August 1999. The population, distributed over an area of 255 ha, was estimated at about 18 * 106 individuals, having a mean length of about 68 mm. Of this number, about 16 * 106 individuals were aggregated into a core area of 51 ha. A subsequent controlled harvest carried out in 33.5 ha of this area in November 2000 produced only 2 * 105 individuals, strongly suggesting that large scale clandestine (illegal) harvesting had occurred since the original population survey. Reseeding of collected scallops was carried out in an interior area of the bay which had low densities of scallops but highly similar physical and chemical seawater characteristics. Post-seeding mortality of the translocated scallops, determined two weeks after the transfer, was 12.5%, with a mean of 2.5 indiv./m² in an 8.2 ha area. The low initial mortality, compared with values in the literature, suggested that the methods of retrieval, transport, and restocking the scallops could serve as a viable repopulation strategy in other areas in the future.