Weaning Ages of Bluegill and Redear Sunfish Fry in Indoor Recirculating Aquaculture Systems

Abstract

AbstractWeaning fry indoors to commercial starter feed reduces the feeding labor and risks related to live food production. Limited work has been done in determining the ideal weaning age in Lepomis species. Our objective was to determine the optimum weaning ages for bluegill Lepomis macrochirus and redear sunfish L. microlophus. Four age‐weaning treatments with four replicates of 300 fish per unit were randomly assigned in 32 tanks. Treatments were initiated at 2, 6, 10, and 14 d post–nest exodus by co‐feeding a commercial feed with live prey for 6 d. Thereafter, fish received only commercial feed until the experiment was terminated at 35 d. Production and survival at 35 d increased as weaning age increased. The production weights (means ± SEs) of bluegills weaned at 2, 6, 10, and 14 d were 4.3 ± 0.3, 18.9 ± 2.2, 27.3 ± 4.6, and 39.0 ± 1.1 g, and those for redear sunfish were 6.5 ± 1.2, 23.6 ± 3.0, 43.7 ± 2.7, and 56.5 ± 4.2 g. Survival rates were 31.3 ± 1.5, 50.2 ± 3.0, 59.8 ± 2.8, 78.9 ± 2.3% and 12.7 ± 2.2, 32.0 ± 1.4, 52.8 ± 2.5, 71.9 ± 2.8% for bluegills and redear sunfish, respectively. Reported feed conversion ratios and individual weights and lengths tended to increase with weaning age, and no differences were observed between fish weaned at 10 d and those weaned at 14 d. Terminal mean weights were 45.8 ± 1.8, 125.9 ± 12.9, 150.6 ± 19.9, and 165.3 ± 8.0 mg for bluegills and 171.9 ± 8.7, 246.4 ± 31.8, 275.9 ± 12.3, and 262.9 ± 21.5 mg for redear sunfish weaned at 2, 6, 10, and 14 d. Abnormal fish were mostly restricted to fish weaned at 2 and 6 d. This study indicated that delayed weaning times improved the production weights of both species owing mainly to increased survival rates.