Identification of blue catfishes

[Silurus]

Rodiles-Hernández, R, JG Lundberg & JP Sullivan, 2010. Taxonomic discrimination and identification of extant blue catfishes (Siluriformes: Ictaluridae: Ictalurus furcatus group). Proceedings of the Academy of Natural Sciences of Philadelphia 159: 67–82.

Abstract

Three species of the Ictalurus furcatus Group (genus Ictalurus) are recognized: I. furcatus, I. meridionalis and I. balsanus. These species are differentially diagnosed by characters of the bony skeleton, fin-ray and vertebral counts, morphometries and coloration. Ictalurus balsanus is distinctive in having a relatively short supraoccipital process, anterior nuchal plate and posterior cleithral process, weakly developed pectoral-fin spine ornamentation, and an elongated posterolateral premaxillary process. Ictalurus furcatus and I. meridionalis are closely similar species but are clearly distinguished by features of the pectoral-fin spine ornamentation, supraoccipital process shape and texture, posterior cleithral process shape, numbers of anal-fin rays and vertebrae, and related proportional measurements of anal-fin and caudal peduncle length. Apparent differences among the three species in maximum size and coloration are also noted. A limited sample of molecular sequence data from the 12S/16S mitochondrial DNA loci is consistent with morphology-based results indicating that I. meridionalis is a species distinct from I. furcatus, and that I. balsanus is the most divergent species of the three. Ictalurus furcatus and I. meridionalis exhibit interriver basin variation in numbers of vertebrae and anal-fin rays.