Group holding impedes compensatory growth of hybrid sunfish

An earlier study with a repeating no-feed/refeed schedule (D2 schedule) eli cited compensatory growth (CG) in age-0 hybrid sunfish (F1: female green su nfish: Lepomis cyanellus X male bluegill L. macrochirus) held individually and fed ad libitum on feeding days. Weight gain under these conditions exce eded that of daily-fed controls. The present study sought to determine whet her similar growth improvement would result when hybrid sunfish were held i n groups and fed to satiation on the D2 schedule. In Experiment 1, age-0 hy brid sunfish were held in groups of 10 fish per 25-1 chamber at 24 degrees C and fed four times daily to apparent satiation on feeding days. Under thi s 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 re sults of the previous study. When age-0 fish were held individually at 24 d egrees C and fed ad libitum on feeding days, those fed on the D2 schedule g ained 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 impedim ent under group holding may be the negative effects of social interactions on food consumption and growth efficiency. (C) 2000 Elsevier Science B.V. A ll rights reserved.