Effect of winter feeding frequency on growth, survival, and fatty acid metabolism of juvenile bluegill (Lepomis macrochirus) and hybrid bluegill (L. cyanellus × L. macrochirus)

Abstract

There has been an increasing global demand for large bluegill (Lepomis macrochirus) and its hybrid (female Lepomis cyanellus×male L. macrochirus) to supply the food-fish market. However, production of market-size bluegill requires producers to overwinter them in temperate regions. Winter fish mortality is widely cited by fish farmers in temperate regions of the U.S. as a major factor that decreases profitability and sustainability. We evaluated the effect of three different feeding frequencies on survival, weight loss, and fatty acid composition of two species of Centrarchids held at a constant low temperature (7–9°C) to simulate winter conditions. Bluegill (1.46±0.06g) and hybrid bluegill (2.58±0.22g) were stocked in separate 603-L recirculating systems configured with 9 tanks each (3 replicate tanks/feeding regime) and fed either twice per week, once per week, or once per month for 13weeks. There were no differences among feeding regimes in final fish weight, survival, weight loss as a percent of initial weight, condition factor, and SGR for either taxon of fish. Survival was high among all treatments (89–98%). Regardless of feeding regime, all fish lost weight. Hybrid bluegill lost less weight (12–17% of initial body weight) than bluegill (18–20%). The concentrations and composition of fatty acids also changed markedly in response to feeding frequency according to canonical discriminant analysis. Fatty acid profiles among initial vs. post-winter bluegills fed at different frequencies were indicative of severe deficiencies in n-6 and n-3 essential fatty acids and preservation of long chain polyunsaturated fatty acids, especially when fish were fed less than twice per week. In conclusion, significant weight loss and reductions in key fatty acids needed for energetic needs were observed in both native and hybrid bluegill, regardless of feeding regime, indicating that the feeding rates examined in this study did not prove beneficial at 7–9°C in preserving winter robustness.