Comparison of Two Biometric Methods for Nonlethal Sex Determination of Alligator Gars

AbstractMcDonald et al. (2013) proposed a morphometry-based method for nonlethal sex prediction of the Alligator Gar Atractosteus spatula. Their method correctly predicted sex to 93% of males and 72% of females tested, but failed to predict the sex of 21% of fish. The authors noted that the method was primarily developed using immature fish from a single Texas population, and as such, recommended further validation and refinement using fish from a broad range of sizes and systems. Therefore, we tested the McDonald et al. (2013) method using 149 fish (standard length (SL) range, 707–1,920 mm) collected from seven Texas populations. Sex prediction based on the McDonald et al. (2013) method improved for both sexes (93% of males and 97% of females); however, sex still could not be predicted for 29% of fish. As a result, we explored the use of a cross-validated, discriminant function analysis (DFA), using the morphometric ratios developed by McDonald et al. (2013), to improve our ability to predict sex of samp...