Hatchery performance attributes of juvenile lake sturgeon fed two natural food types

The use of stocking programs to rehabilitate depressed populations of lake sturgeon Acipenser fulvescens requires the optimization of early life stage growth in hatchery settings. We evaluated the performance of juvenile lake sturgeon fed different proportions of two natural food types - adult brine shrimp Anemia spp. and larval bloodworms Chironomus spp. - over a 10-week laboratory experiment. The following live diet treatments were provided: (1) 100% bloodworms; (2) 75% bloodworms: 25% brine shrimp; (3) 50% bloodworms: 50% brine shrimp; (4) 25% bloodworms: 75% brine shrimp; and (5) 100% brine shrimp. Lake sturgeon growth was positively related to bloodworm content in the diet and was significantly different among treatments. Although the initial sizes of fish were similar, mean fork length and wet weight were greatest for the 100% bloodworm treatment (183.1 mm and 37.5 g, respectively) and lowest for the 100% brine shrimp diet (118.4 mm and 9.5 g) by the end of the study. Mean specific and absolute growth rates in length (0.93% and 1.28 mm/d, respectively) and weight (2.61% and 0.45 g/d) were greatest for the 100% bloodworm diet, followed by the other treatments in order of decreasing amount of bloodworms in the diet. Percent weight gain (525%) and food conversion efficiency (67%) were also greatest for the 100% bloodworm diet, followed by the other treatments in order of decreasing dietary bloodworm content. Whole-body protein (13.9%). lipid (2.5%), and gross-energy (3.77 kJ/g) content were greatest for fish fed 100% bloodworms, with these proximate-composition measures also ranked in order of decreasing dietary bloodworm content for the other treatments. We recommend that juvenile lake sturgeon reared in hatchery environments be fed high proportions of bloodworms to maximize growth, body size, and lipid content for rehabilitation stocking programs.