Abundance and harvest strategy of three species of clam (Bivalvia: Veneridae) located in new fishing banks in the Gulf of California

Abstract

Clams of the family Veneridae in northwest Mexico have traditionally been exploited by small-scale fisheries. Despite their socioeconomic importance for coastal communities in the region, most catch zones are currently in decline due to a lack of harvest control regulations that would impede the depletion of local fishing banks. In Puerto Libertad, in the northern reaches of the Gulf of California, banks of commercially unexploited clam species, including Megapitaria aurantiaca, M. squalida and Dosinia ponderosa, were discovered. The adequate management and exploitation of these banks requires developing basic knowledge regarding the abundance of the species and establishing reference points to determine clear, simple harvest regulations. The goal of this study was to identify population abundance in these banks and ascertain the parameters of the life history of the species found there in order to propose a harvest strategy that will allow the sustainable exploitation of this resource. A total of 288 transects were conducted in the two clam banks to identify species density. Abundance was determined using a geostatistical method. The relative cohort biomass-at-length was estimated to evaluate the effect of different lengths of first capture on the remaining biomass. Based on these data, two harvest control regulations were proposed: a maximum catch (Cmax) of 10% of the total estimated biomass, and a minimum optimal catch size (Lc). The abundance estimates were M. squalida (266,293–381,881 individuals); D. ponderosa (2,779,100–3,455,597); and M. aurantiaca (408,783–447,391). The harvest control regulations proposed are: M. squalida, Cmax = 2.98 t and Lc = 50.33 mm; D. ponderosa, Cmax = 49.67 t and Lc = 103.44 mm; and M. aurantiaca, Cmax = 15.87 t and Lc = 80.85 mm. These results are important as reference information for implementing harvest strategies in clam-fishing banks, and as a contribution to the management and sustainable exploitation of fisheries in the region.