Defining the stock of Chilean scallop Argopecten purpuratus

• Main Author: Pickerell, T. K. D.
• Published: Swansea University 2003
• Subjects: 636
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638529

The Chilean scallop <i>Argopecten purpuratus </i>is a commercially important cultured bivalve in both Chile and Peru with annual yields of approximately 37,000 tons. At present no studies have been carried out to investigate the population genetics of this species and therefore genetic management cannot currently be successfully practised. The aims of this study were to provide baseline data for genetic improvements of stocks and the conservation of genetic resources. This was to be achieved by assessing the genetic diversity using microsatellites and mitonchondrial DNA genetic markers. A species-specific mitochondrial DNA primer pair was successfully developed using sequence amplified from PCR primers developed for the clam complex Lasaea. PCR primers were developed for three microsatellite loci successfully isolated from <i>A. purpuratus</i> and one locus was variable and therefore suitable for phylogenetic analysis. The genetic variation of over 150 individual scallops from 5 populations were assayed and a variety of tests were performed on the allele frequencies and sequences. The sequence analysis results provide evidence supporting the existence of two separate, genetically differentiated, stocks in Chile: The Tongoy Bay stock (consisting of the Coquimbo and La Serena samples) and the Antofagasta/Concepcion/Valparaiso stock. It is hypothesised that the anthropogenic introduction of scallops from Tongoy Bay and the Mejillones and the Rinconda stocks into newly established cultures around Puerto Montt combined with the hydrology of the region have acted to cause an extreme form of range expansion. The differentiation observed between the stocks, is considered to result from the replacement of original wild scallops in Tongoy Bay by individuals descended from larvae from cultured individuals. In addition, tests of population expansion suggest recent large increases in scallop numbers. This finding supports the hypothesis of large periodic El Niño induced expansions of <i>A. purpuratus </i>numbers, previously only documented through increases in scallop catches (up to 60% growth).