Genetic evidence of isolation by distance and impact of impoundments on genetic diversity of riverine channel catfish

This study used microsatellite loci to provide evidence of isolation by distance and an effect of artificial impoundments on the genetic diversity of Channel Catfish Ictalurus punctatus from the Wabash and Ohio rivers. The Wabash River is the longest free-flowing river east of the Mississippi River in the USA, and the Ohio River is highly impounded, yet both rivers support large Channel Catfish fisheries. There was a significant positive relationship between genetic differentiation and geographic distance indicating isolation by distance. Clustering with the programs, STRUCTURE and GENELAND, and principal component analysis revealed multiple genetic clusters, and several sites had results consistent with adults existing as mixtures of genetic groups. These results suggest that the rate of straying among reproductive sites or dispersal is dependent on geographic distance. Channel Catfish from the unimpounded Wabash River had higher genetic diversity (H_o and H_e) than that from the impounded Ohio River. The impoundments had discordant effects on genetic structure; two site comparisons across a damwere differentiatedmore strongly than would be expected by geographic distance, whereas genetic differentiation was not detected in another comparison across a dam. Thus, the effect of artificial impoundments on Channel Catfish biology may be affected by river or site-specific characteristics, and the presence of genetic differentiation may be minimized by large population sizes.