Evaluation of Walleye Fingerling and Fry Stocking in Rathbun Lake, Iowa

Abstract

Fry and fingerling stockings of walleye Stizostedion vitreum at Rathbun Lake were evaluated from 1984 to 1989 to determine the stocking strategy necessary to triple the lake's walleye biomass. Daily loss of fry for the first 25 d ranged from 12% in 1984 to 26% in 1987. In August cove samples, densities of walleyes stocked as fry were estimated at 2–14/acre, whereas October mark-recapture estimates were 2–27/acre. Fingerlings stocked in October were either extensively cultured in Spirit Lake nursery lakes or were intensively cultured at Rathbun Hatchery on a pelleted diet. In terms of overwinter survival, fingerlings stocked as fry were superior to those stocked as fingerlings in October. Of the fingerlings stocked in October, Rathbun walleyes (reared in tanks on pellet diet) had greater survival than did fingerlings from nursery lakes. Survival was 2–11 times greater for intensively cultured walleye fingerlings. Nursery lake walleyes probably had lower survival rates because of poorer body condition and hauling stress. Stocking 2,000 fry/acre and 5–13 fingerlings/acre since 1984 has resulted in a sexually mature population of 8,400 walleyes with a mean fish weight of 3.7 lb. Biomass of walleyes longer than 17 inches was 0.9 lb/acre in 1987 and increased to 2.8 lb/acre in 1989; thus, the population biomass was tripled and the project goal was achieved.