TESTING BIOENERGETICS MODELS UNDER FEEDING REGIMES THAT ELICIT COMPENSATORY GROWTH

We tested bioenergetics model predictions of fish growth and food cons umption under feeding regimes that elicited compensatory growth (CG) r esponses and for control fish fed ad libitum daily. Three treatment gr oups of seven juvenile hybrid sunfish (F-1 hybrid of female green sunf ish Lepomis cyanellus X male bluegill L. macrochirus) received repeati ng cycles of no feeding and refeeding; fixed no-feed periods of either 2, 4, or 14 d distinguished the treatment groups. The no-feed periods induced CG and were immediately followed by days of ad libitum refeed ing. The refeeding periods for each treatment group were continued unt il the group's mean daily consumption no longer exceeded that of the c ontrols, after which another no-feed period began. Bioenergetics model predictions of cumulative consumption and fish weight in 105-d experi ments were not significantly different from observed values in the con trol group (2-3% model error). However, the model underestimated cumul ative consumption (18-25%) and overestimated fish weight (24-37%) in e ach of the treatment groups. Compensatory growth has considerable pote ntial in aquaculture, and our findings show that bioenergetics models will require modification to account for the effect of feeding history on fish growth and consumption before such models can be used to pred ict CG responses in aquaculture. The extent to which CG occurs in nonc aptive fishes is uncertain, although developing evidence suggests that it may be common. The presence of CG in noncaptive fishes could resul t in significant errors in model estimates of their food consumption a nd growth.