Survey of Swim Bladder Inflation in Walleyes Reared in Hatchery Production Ponds

Abstract

Abstract We examined pond-reared fingerling walleyes (Stizostedion vitreum) for inflation of the swim bladder at harvest. We evaluated 120,064 fish from 15 facilities in nine states during 1989, 1990, and 1993. Samples of walleye were collected from 188 ponds, and only 3.5% (4,229) of the fish examined lacked an inflated swim bladder during the 3-year period. Walleyes with uninflated swim bladders were observed at each facility during one or more years. Of the 188 ponds, 53.7% (101) contained walleyes that lacked inflated swim bladders, and these fish (after freezing) were shorter and lighter in weight and had less body fat than walleyes with inflated swim bladders. There appeared to be no relationship between size of fish at pond harvest and the incidence of swim bladder inflation in any pond. Incidence of uninflated swim bladders reached 55% in one pond. Although only a small percentage of walleyes overall lacked an inflated swim bladder in this survey, we feel that walleye fingerlings should be sampled...