Population dynamic of Donax denticulatus (Bivalvia: Donacidae) at Carenero Beach, Southeastern Cuba
Bivalve molluscs of Donax genus are a very important component of macro-invertebrate assemblages of sandy beaches, and some species are of commercial value in different countries. Although in Cuba Donax denticulatus is not a currently exploited species, the information concerning a stock assessment is a basic step for future use of this resource. With the aim to generate new data on this species structure, growth and secondary production, monthly samples of D. denticulatus were taken from a beach of the Southeastern coast of Cuba, from February to December 2008. Samples were taken from four stations located along the beach; three strata were marked (P1, P2 and P3) per station across the intertidal zone. Three replicated samples of sediments were taken from each stratum with a 0.025m2 PVC core and were posteriorly sieved with a 1mm mesh. Histograms of shell length were constructed based on 1mm intervals and growth parameters were estimated using ELEFAN I routine of FISAT. Mean density ranged from 146.67-855.55ind./m2 and no differences were found among months (ANOVA, p>0.05) but among strata (Scheffé, p<0.05). An association of recruits, young and adults abundances with the strata (X2, p<0.01) was found. Most of the recruits were found in the upper strata while young and adult individuals were abundant in the mid-lower strata. Size frequency histograms of this population showed recruitment between March-June. Growth parameters estimated by Von Bertalanffy were L∞=27.5mm and K=1.5/year; and the life spam was estimated in 1.5 years. Using the length-converted catch curve, the mortality rate (Z) was estimated in 4.97/year. Based in terms of Ash free dry mass (AFDM), mean biomass was estimated in 0.47g/ m2.year and the somatic production in 12.4g/m2.year. The renewal rate (P/B) estimated for this population was 26.38, the highest among other Donax populations. High densities, fast growth and high somatic production indicate that this population can be exploited for fishing purposes for which some management measures are proposed.
Keywords: donax, population structure, growth, production, biomass, sandy beaches, cuba