Realized heritabilities and genetic correlation after dual selection for total weight and shell width in catarina scallop ( Argopecten ventricosus)

Abstract

A one-generation selection for total weight and shell width at age 1 year in catarina scallop, Argopecten ventricosus, was done on two lines to estimate direct and correlated responses to selection, realized heritabilities, and the realized genetic correlation between these two traits. For both lines, two experiments were done to estimate response, one after inducing spawning of field-conditioned scallops, and the second after conditioning the same individuals from the first experiment for spawning in the laboratory. Responses to selection were significant for both direct traits. A significantly higher correlated response of shell width when selection was on total weight was seen, whereas the correlated response for total weight when selection was on shell width was small or zero. Realized heritability of total weight was higher (0.33±0.08 to 0.59±0.13) than that of shell width (0.10±0.07 to 0.18±0.08) regardless of the experiment. Estimates of the genetic correlation between the two traits varied widely between experiments (1.25±−0.22 in experiment 1 and 0.33±0.31 in experiment 2). Regardless of this, we concluded there must be a high genetic correlation between these two traits, evidenced by the high correlated response of shell width when selecting on total weight. Correlated responses larger than direct responses as those seen for shell width result because the accuracy of selection for total weight to indirectly improve shell width ( r a h TW) is larger than the accuracy of direct selection for shell width ( h SW).