Group holding impedes compensatory growth of hybrid sunfish

Abstract

An earlier study with a repeating no-feed/refeed schedule (D2 schedule) elicited compensatory growth (CG) in age-0 hybrid sunfish (F1: female green sunfish, Lepomis cyanellus×male bluegill L. macrochirus) held individually and fed ad libitum on feeding days. Weight gain under these conditions exceeded that of daily-fed controls. The present study sought to determine whether similar growth improvement would result when hybrid sunfish were held in groups and fed to satiation on the D2 schedule. In Experiment 1, age-0 hybrid sunfish were held in groups of 10 fish per 25-l chamber at 24°C and fed four times daily to apparent satiation on feeding days. Under this regime, fish fed according to the D2 schedule gained less weight than the controls ( P<0.10). Experiment 2 was run in an effort to duplicate the results of the previous study. When age-0 fish were held individually at 24°C and fed ad libitum on feeding days, those fed on the D2 schedule gained significantly more weight ( P<0.10) than the controls. These results indicate that group holding in combination with satiation feeding impedes the full expression of the CG capacity of hybrid sunfish. The major impediment under group holding may be the negative effects of social interactions on food consumption and growth efficiency.