Evaluation of Walleye Fry Stocking in Clear Lake, Iowa, by Alternate-Year Planting

Stocking of 5,000 to 9,500 walleye fry, Stizostedion vitreum vitreum (Mitchill), per acre in Clear Lake, Iowa, in the even-numbered years resulted in larger numbers of walleyes in those year classes than in the odd-numbered year classes (1949 to 1957) when no walleye fry were stocked. This conclusion was reached because (1) more walleye fingerlings were collected by seining beach areas in years of stocking than in years of no stocking; (2) age distribution of walleyes collected in experimental gill nets each year, 1947 to 1958, indicated that the even-numbered year classes were more abundant than the odd-numbered year classes; (3) catch of walleyes in even-numbered year classes, computed for an equal amount of experimental gill-netting, outnumbered those in year classes when there was no fry stocking by 3 to 1 during the first 6 years of the life of the fish; and (4) estimates of population by tagging and recovery techniques indicated that the 1950 year class was much greater than the 1949 year class.