I am the KDFWR biologist in charge of the native strain walleye research on the Rockcastle River. Benjy Kinman asked me to respond to this thread in response to Jim Dicken’s inquiry. Through extensive genetic testing we have determined that the walleye in the Rockcastle River are “pure” southern strain walleye that are native to Kentucky. Since 2002, we have been conducting a supplemental native walleye stocking program in the Rockcastle River and have also been stocking native strain walleye in Wood Creek Lake (a tributary of the Rockcastle River). The native strain walleye population in Wood Creek Lake is now a source of mature walleye broodstock and frees us from having to remove as many walleye from the low density population in the Rockcastle River. These are the ONLY two water bodies where native walleye have been stocked. All other walleye stocked by the KDFWR around the state are northern strain or also called “Erie” strain.
The KDFWR collects northern strain broodfish from shoal areas of the Big South Fork arm of Lake Cumberland each spring. Northern strain walleye from the lake typically migrate only as far as the first or second shoal. Fish collected in these areas are genetically tested before being used for broodstock. How far up the Big South Fork arm these collections take place is determined by the level of Lake Cumberland at the time. Several native strain walleye have been collected in the Big South Fork in years when the lake has been high and electrofishing boats have been able to get above Yamacraw into places that are normally above lake influence. An extensive electrofishing survey looking for walleye in the upper Big South Fork has not been conducted because of inaccessibility, but there is a fair likelihood that a native strain walleye population exists there. We have no indication that native strain and northern strain walleye have interbred here either.
For many years the KDFWR stocked the upper Cumberland River (above the falls) with northern strain walleye. We discontinued all walleye stockings above the falls in the Cumberland River after 2004. We intend to monitor the river for any natural reproduction of existing northern strain walleye. Barring this, we may be able to re-introduce native strain walleye to the upper Cumberland River in a few years. We are also examining other rivers in the state where native strain walleye were native and have suitable conditions for re-introduction. The main condition that we are trying to avoid is a situation where the two strains could hybridize in large numbers and then contaminate our pure stock. Some may wonder about that because I already mentioned that they have been found together in the Big South Fork and there is nothing keeping northern strain walleye from migrating out of Lake Cumberland up into the Rockcastle River. The speculation is that there are aspects of their respective reproductive biology that keeps them apart in these specific situations (or at least hybridize so rarely we cannot detect it). We feel it is prudent to not push the envelope by stocking native strain walleye in areas where northern strain walleye are already present, specifically Lake Cumberland. Hybridization could occur on a large scale in the lake and then these hybrid walleye may have more of a propensity to migrate into the Rockcastle River in large numbers, thereby contaminating our pure native strain walleye stock and potentially permanently losing this genetic integrity.
Dave Dreves
Fisheries Research Biologist
KY Dept of Fish and Wildlife Resources
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