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

A one-generation selection for total weight and shell width at age 1 year i n catarina scallop, Argopecten ventricosus, was done on two lines to estima te direct and correlated responses to selection, realized heritabilities, a nd the realized genetic correlation between these two traits. For both line s, two experiments were done to estimate response, one after inducing spawn ing of field-conditioned scallops, and the second after conditioning the sa me individuals from the first experiment for spawning in the laboratory. Re sponses to selection were significant for both direct traits. A significant ly higher correlated response of shell width when selection was on total we ight was seen, whereas the correlated response for total weight when select ion was on shell width was small or zero. Realized heritability of total we ight 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 experi ments (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 b etween these two traits, evidenced by the high correlated response of shell width when selecting on total weight. Correlated responses larger than dir ect 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)). (C) 1999 Elsevier Science B.V. All rights reserved.