Growth and biannual recruitment of the black scallop Chlamys varia (L.) in lanveoc area,Bay of Brest

Data on growth of the black scallop Chlamys varia (L.) were obtained by taggine, raft cage rearing, reading winter growth rings, and analysis of length-frequency distributions. Von Bertalanffy growth curves were fitted to each set of data by least-squares regression techniques involving no transformation of variates. The results obtained by the different methods are comparable except for those obtained by length-frequency distribution analysis. Length frequency distribution analysis seems to be complicated by the presence of a biannual recruitment. Counting growth rings seems to be a more accurate and easier method for growth estimates. The sizes at rings are different for individuals born in spring and for those born in autumn; the growth curves derived for these two types of animals remain different throughout their whole life. The relative proportions of individuals originating from each of the two recruitment groups have remained remarkably homogeneous for the last five years. Comparative study of the allometric relationships between length and width of the shell of the animals from the two recruitment groups showed no significant difference.