A Genetic Assessment of Ohio River Walleyes

Abstract

Walleyes Sander vitreus from nine Ohio River pools were examined by means of two independent restriction fragment length polymorphism (RFLP) analyses of mitochondrial DNA, allozyme analysis of nuclear DNA, and microsatellite analysis of nuclear DNA. The primary objective of this project was to document genetic variation and population structuring in walleyes among the nine pools analyzed. Both RFLP analyses revealed the presence of a distinct haplotype that was most abundant in walleyes collected from two tailwaters in the upper Ohio River (river miles 54 and 84), suggesting a remnant native population. The allozyme analysis also revealed differentiation between walleyes with the two haplotypes, even though there were no fixed differences. The microsatellite analysis indicated highly significant structuring among the nine pools analyzed. A lack of microsatellite differentiation between the two haplotypes detected in the same pool suggests that the fish are freely interbreeding. If the unique haplotype is from a remnant native stock of walleyes in the Ohio River, it could serve as a genetic marker to establish a broodstock for stocking walleyes in the upper Ohio River drainage. The second objective of the project was to evaluate the accuracy of field identifications of walleyes, saugers S. canadensis, and their hybrid, saugeyes, and to determine the direction of hybridization. Twenty-seven percent of the fish identified as walleyes were misidentified (10% were F _X hybrids and 17% F₁ hybrids). All F₁ hybrids were from walleye females and sauger males.