MORPHOLOGICAL AND ELECTROPHORETIC EXAMINATION OF STIZOSTEDION SAMPLESFROM LEWIS AND CLARK LAKE, SOUTH-DAKOTA

Cellulose acetate electrophoresis was used to screen muscle and liver samples from 50 Stizostedion individuals collected from Lewis and Clar k Lake, South Dakota to determine the degree of hybridization between walleye (Stizostedion vitreum) and sauger (Stizostedion canadense) and to assess the accuracy of morphological identification. Electrophoret ically, 40 fish were identified as sauger, five as walleye, and five a s hybrids. Thus, there was approximately a 10% hybridization rate for this sample from Lewis and Clark Lake. Identification based on morphol ogical characteristics significantly (P < 0.05) overestimated the perc entage of hybrids compared to the electrophoretic analysis. Morphologi cally, 34 fish were identified as sauger, seven as walleye, and nine a s hybrids. Eight fish (16%) were incorrectly identified using external traits. Because the electrophoretic and morphological identification differed, biologists should be cautious when monitoring these fishes o r when using wild broodstock from systems in which both species are pr esent.