A Standardized Procedure for Internal Sex Identification in Lepisosteidae

Abstract

During population dynamic and reproductive biology research on three species of Lepisosteidae (i.e., alligator gar Lepisosteus spatula (also known as Atractosteus spatula), longnose gar L. osseus, and spotted gar L. oculatus), we determined that misidentification of sex through gross examination of the gonads was probable. During gross examination of the gonads of all three species, postspawning and juvenile ovaries frequently resembled testes due to the envelopment of the ovaries by fatty tissue. We examined the gonads and gamete release pathways of 598 individuals and found that gamete release pathways (i.e., oviduct in females and vasa efferentia in males) were differentiable and can be used reliably in all seasons for all reproductive stages of the three species. Misidentification of sex can lead to inaccurate estimation of sex ratios and sex-dependent mortality and growth rates. Accurate estimates of Lepisosteidae population structure and vital rates are needed for successful conservation and management actions. To avoid misidentification of sex, we propose the use of gamete release pathways for sex identification in Lepisosteidae.