Sexual Dimorphism in Alligator Gar

Abstract

AbstractThe Alligator Gar Atractosteus spatula is currently imperiled due to habitat alterations and overharvest within much of this species’ range. Recent interest in improving management for this species within the USA and Mexico has spurred new creel restrictions, spawning area closures, and stocking programs, along with increased research on life history and population dynamics. These management and research measures can be improved by a noninvasive method for determining sex. Previous methods have required sacrificing the fish (for internal anatomy confirmation) or using costly and time‐consuming assays from a specialized laboratory. Evidence from other gar species suggests that sex determination is possible by examining sexually dimorphic external characters. We evaluated the utility of 13 morphological measurements for determining the sex of Alligator Gars of known gender (n = 117; SL range, 591–1,255 mm). Discriminate analysis identified two influential variables (snout length and caudal peduncle height) as sexually dimorphic. Univariate analyses identified three variables as sexually dimorphic (head length, snout length, and anal fin base length). Sexually dimorphic variables were used with SL to develop a method using serial body ratios (SL/snout length) followed by (snout length/anal fin base length) to identify sex in Alligator Gar to 93% accuracy in males and 72% accuracy in females.Received April 1, 2013; accepted June 3, 2013