Preliminary analysis of the genetic variability of two natural beds of the scallop Euvola ziczac (Linnaeus, 1758) in Brazil

Euvola ziczac (formerly Pecten ziczac), a simultaneous hermaphroditic scallop was heavily fished in Brazil between 1972 and 1980. The production peaked in 1980 with 8,800 tons and was followed by the total collapse of the resource. In order to investigate the possible loss of genetic variability of the stock associated to overfishing and self-fertilization, the polymorphism of phosphoglucomutase (PGM) and glucose phosphate isomerase (GPI) was analyzed by electrophoresis of the adductor muscle of scallops from Sao Francisco (26 degrees 20.583'S; 48 degrees 16.507'W) and Bom Abrigo (25 degrees 28.735'S; 47 degrees 37.621'W) beds; the southern and northern extremes of the scallop fishing ground, respectively. Animals from Sao Francisco showed a strong deficiency of heterozygosity for GPI and PCM. In addition, PGM showed *exclusive alleles for each bed. Such results coupled with other information about the species suggested the following hypothesis: a) the stock was a metapopulation with at least two populations; b) some reproductive isolation might be occurring which might be influenced by conditions of larval transport and by the extremely low densities of scallops; c) presently, the stock seemed to be mostly maintained through self-fertilization; d) Sao Francisco could constitute a source-area, contributing with larvae and recruits to Bom Abrigo and other areas; e) both beds were suffering a genetic homogenization more evident in Sao Francisco. Such hypothesis needed to be investigated in order to furnish guidelines for future programs of recovery and management of the resource.