Growth, Feed Conversion, and Protein Utilization of Female Green Sunfish × Male Bluegill Hybrids Fed Isocaloric Diets with Different Protein Levels

A 10-week feeding trial was conducted in aquaria to evaluate protein requirements of juvenile (4.7-g) hybrids of female green sunfish (Lepomis cyanellus) and male bluegills (Lepomis macrochirus). Three Isocaloric diets containing 26, 31, or 37% protein were evaluated for effects on fish growth, feed conversion, protein utilization, and body composition. Fish fed the 37% protein diet had significantly higher (P < 0.05) body weights, percentage weight gains, and specific growth rates than fish fed other diets. There were no significant differences (P > 0.05) among diets in protein efficiency ratio (fish weight gained/protein weight fed). Fish fed the 26% protein diet had a significantly higher (P < 0.05) feed conversion (feed weight fed/fish weight gained) than fish fed the 37% protein diet. These results suggest that the use of higher-protein feeds (35% or greater), rather than the 32% protein catfish feed that is often fed to bluegill hybrids, may improve growth performance and production potential of this hybrid.