Abstract

Extensive overlap in external morphology among species of smoothhound sharks (genus Mustelus) has made identification of individual species difficult. Consequently, verifying the distribution of individual species in the Gulf of Mexico (Gulf) and planning effective strategies for their management and conservation are problematic. Phylogenetic analysis of sequences of the mitochondrial-ly-encoded NADH-2 gene identified three reciprocally monophyletic lineages, which correspond to three different species of smoothhound sharks in the Gulf, a result verified via genotypes at nuclear-encoded microsatellites. When adult specimens (both sexes) were separated based on genetic characteristics, we discovered differences in external morphology that permit reliable species identification in the field. Here, we present a diagnostic key to distinguish among smoothhound sharks (Mustelus canis, Mustelus sinusmexicanus and Mustelus norrisi) in the Gulf. Results of this study should prove useful in management and conservation efforts for smoothhound sharks resources in the Gulf.

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