Some Genetic Characteristics of Three Walleye Stocks in Iowa and the Impact of Fry Stockings in the Cedar River

Fry stockings of walleye Stizostedion v. vitreum into the Cedar River, Iowa began in the early 1950\u27s, and two studies of the success of these plants gave conflicting results. The objectives of my study were to identify some genetic characteristics in three stocks of walleye and to utilize these characteristics to assess the genetic impact of fry stockings in the Cedar River. Electrophoretic analysis of malate dehydrogenase (MDH) and isocitrate dehydrogenase (IDH) was completed for walleye stocks from the Mississippi and Cedar Rivers, and Big Spirit Lake, Iowa. Phenotypic frequencies of Mdh - B2 and Mdh - B3 were as follows: Mississippi River walleye, 83 and 17%, respectively; Cedar River walleye, 71 and 29%, respectively; and Spirit Lake walleye, 19 and 81%, respectively. Chi-Square testing of these frequencies demonstrated that Spirit Lake fish differed significantly from Mississippi (P\u3c0.001) and Cedar River fish (P\u3c0.05), but there was no difference in frequencies between the two river walleye populations. Phenotypic frequencies of Idh - B1 and B2 were 54 and 46% for Mississippi River fish; 65 and 35%, respectively, for Spirit Lake fish; and, 65 and 35 % for Cedar River walleye, respectively. Chi-square testing indicated that these frequencies were similar (P\u3e0.05). My study indicated that there are some genetic differences between walleye stocks in the two Iowa rivers and Big Spirit Lake. It is probable that the native Cedar River and Mississippi River stocks are genetically similar, particularly since the former is a tributary to the latter. Also, fry stockings of Big Spirit Lake walleye, and their progeny, have contributed only about 19% to the Cedar River population. Fry stockings are less successful than was once thought, and a more refined stocking program is needed