USE OF COMPENSATORY GROWTH TO DOUBLE HYBRID SUNFISH GROWTH-RATES

We studied the use of compensatory growth (CG) to grow fish larger tha n control fish that were fed every day without restriction. Five treat ment groups of 10 juvenile hybrid sunfish (F-1 hybrid of female green sunfish Lepomis cyanellus x male bluegill L. macrochirus) received rep eating cycles of no feeding and refeeding; fixed no-feed periods of ei ther 2, 4, 6, 10, or 14 d distinguished the treatment groups. No-feed periods elicited the CG state and were immediately followed by days of ad libitum refeeding. Refeeding periods within each treatment group ( D2, D4, D6, D10, or D14) were continued until mean daily food consumpt ion by fish no longer exceeded that of controls fed ad libitum every d ay (i.e., ad libitum refeeding was continued for as long as hyperphagi a persisted, then another no-feed period began). Fish in two groups, D 2 and D14, consumed more food and significantly outgrew controls by 2 and 1.4 times, respectively, in 105-d experiments. Gross growth effici ency (GGE, fish weight gained/weight of all fish consumed) did not dif fer among the control and treatment groups over full experimental peri ods; however, GGE was higher than controls during some refeeding perio ds in group D14 (i.e., when CG was active). Findings show that the CG response can be exploited in some fishes to cause them to substantiall y outgrow conspecifics that are fed every day without restriction, wit h no loss of growth efficiency. Our use of hyperphagia to gauge durati ons of refeeding periods was critical to achieving growth improvements through CG.