Heritability of juvenile growth for the hard clamMercenaria mercenaria

The heritability of juvenile growth in the hard clamMercenaria mercenaria (L.) sampled from Wellfleet Harbor, USA, in 1987, was analyzed in two experiments using standard quantitative genetic methods. In the first experiment, culture density was not controlled and was found to have a significant impact upon the non-additive genetic component of growth, possibly through genotype-environment correlation. Variable clam density appeared to have little impact on the additive genetic variance component. Estimates of the narrow sense heritability, calculated from the additive genetic component, ranged from 0.72 (±0.32) to 0.91 (±0.17). Culture density was controlled in the second experiment. The narrow sense heritability estimate from this experiment was 0.37 (±0.13). These estimates suggest that selection, either natural or artificial could bring about rapid change in the mean phenotype(s) of juvenile growth characteristics in hard clams.Contribution no. 793 from the Belle W. Baruch Institute for Marine Biology and Coastal Research