A comparative study of samples of the bivalve Ruditapes philippinarum (Adams et Reeve, 1850) from populations and shell assemblages

Abstract

According to the results of a comparative analysis of the size and age structures of samples from a population of the bivalve mollusk Ruditapes philippinarum (Manila clam) and from shell assemblages of this species, the possibility of data acquisition on populations using samples from shell assemblages was assessed. A considerable coincidence of these parameters after taking the losses of small individuals during formation of shell assemblage into account, which depended on the location and conditions of assemblage formation, was recorded. Due to the good level of preservation of the shells of older individuals, the sample from the assemblage gave a more comprehensive appreciation of the maximum size and life span of the species than the sample of live mollusks from the natural habitat. Samples from shell assemblages may be used for growth rate estimation of clams without catching live individuals, as the results from studying the linear growth of mollusks based on samples from live populations and from shell assemblages did not differ significantly. Samples from many-year shell accumulations can also be useful for revealing the periods of the highest death rates, the most vulnerable periods in the ontogenesis of the mollusks, and, in some cases, the causes of their death.