Survival, growth and abundance of pellet-reared and minnow-reared muskellunge stocked in northwestern Iowa

Recent advances in artificial feeding techniques have increased the numbers and reliability of fingerling production of muskellunge Esox masquinongy in Iowa. Most of the muskellunge fingerlings produced in Iowa since 1984 were raised on dry pelleted feed. We compared the survival of pellet-reared fingerlings with traditional minnow-reared fingerlings stocked into Spirit and West Okoboji lakes in northwest Iowa. Beginning in 1991, all muskellunge fingerlings were marked with freeze brands to differentiate the type and year that fingerlings were stocked. Adult muskellunge were caught each spring with 360-ft, 2.5-in-bar-mesh gill nets. All muskellunge caught were examined for brands, individually marked with visual implant tags, and released into the same lake as captured. Abundance and survival of stocked fingerlings to year-classes were estimated from recaptures of branded and individually marked muskellunge. In most years none of the pellet-reared fingerlings survived. The poor survival of these fish was most likely due to a combination of poor health, poor color (camouflage barring was muted and virtually nonexistent), and small size (6–9 in total length, TL). Minnow-reared muskellunge fingerlings were much larger (10–13 in TL), displayed strong camouflage barring and no apparent nutritional problems, and survived much better than pellet-reared fish. Minnow-fed fingerlings stocked in the spring survived much better than those stocked in the fall. One spring stocking of only 572 fish more than doubled the muskellunge population in West Okoboji Lake. Such success with stocking muskellunge in the spring could drastically change stocking strategies in Iowa; fewer fish may need to be stocked, and management objectives could be met without annual stockings.