Genetic Diversity and Structure of Channel Catfish from Continental Waters of Mexico

Mexico is the native site of 10 species of the genus Ictalurus, among which the Channel Catfish I. punctatus has great presence in worldwide aquaculture. Wild populations of catfish not only constitute a biological resource but have a great potential for aquaculture. Recently, this species was classified as an invasive organism by the Mexican government. The aim of this study was to determine the structure and genetic diversity of Channel Catfish belonging to native and introduced freshwater populations within Mexico. Using 11 DNA microsatellite loci, we analyzed 292 fish sampled from four rivers and five reservoirs. Observed heterozygosity values ranged between 0.66 and 0.80. The genetic distance analysis showed low to high differentiation among populations (overall genetic differentiation index F _ST  = 0.14). Bayesian coancestry analysis identified two ancestral groups. A single management population on central Tamaulipas can be suggested. The findings of the present study provide the basis for future characterization of productive traits of Mexican Channel Catfish populations in order to use the species as a breeding source for aquaculture. The lower Rio Grande population is one of the most ancient and ecologically relevant Channel Catfish populations in Mexico, and this study identifies it as the most vulnerable. Free-living populations of Channel Catfish, although they have been heedlessly spread, constitute a valuable natural resource that deserves our best effort to preserve.