Functional Maturity and Terminal Molt of Male Snow Crab, Chionoecetes opilio

Abstract

Bivariate and multivariate analyses of allometric relationships between chela size and carapace size of snow crab, Chionoecetes opilio, show that mature males are recognizable by morphometry. The most simple procedure is to plot logarithms of chela height (Ch) against logarithms of carapace width (Lc). Data from mature and immature males fit into two distinct ellipses with parallel major axes. The discriminant function Y = −0.78893 loge. Lc + 0.614488 logeCh + 1.76051 will assign individuals to the correct groups in 99% of cases (for mature males: Y > 0). Spermatophores are present in the vasa deferentia of all males larger than 60 mm Lc. The molt to morphometric maturity occurs later at Lc sizes ranging from 60 to 120 mm; it is identified as final. Only morphometrically mature males larger than 96 mm Lc have been observed to mate efficiently with multiparous females in intermolt and be functionally mature. In the catch, as many as 40% of males larger than the minimal legal size of 95 mm can be immature.