Use of Compensatory Growth to Double Hybrid Sunfish Growth Rates

Abstract
We studied the use of compensatory growth (CG) to grow fish larger than control fish that were fed every day without restriction. Five treatment groups of 10 juvenile hybrid sunfish (F1 hybrid of female green sunfish Lepomis cyanellus × male bluegill L. niacrochirus) received repeating cycles of no feeding and refeeding; fixed no‐feed periods of either 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, D 10, or D14) were continued until mean daily food consumption by fish no longer exceeded that of controls fed ad libitum every day (i.e., ad libitum refeeding was continued for as long as hyperphagia persisted, then another no‐feed period began). Fish in two groups, D2 and D 14, consumed more food and significantly outgrew controls by 2 and 1.4 times, respectively, in 105‐d experiments. Gross growth efficiency (GGE, fish weight gained/weight of all fish consumed) did not differ among the control and treatment groups over full experimental periods; however, GGE was higher than controls during some refeeding periods 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 substantially outgrow conspecifics that are fed every day without restriction, with no loss of growth efficiency. Our use of hyperphagia to gauge durations of refeeding periods was critical to achieving growth improvements through CG.

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