THE ENERGETICS OF STARVATION AND GROWTH AFTER REFEEDING IN JUVENILES OF 3 CYPRINID SPECIES

Experiments were conducted to monitor changes in body mass and metabolic energy expenditure before, during, and after periods of starvation in juveniles of three species of cyprinids: Leuciscus cephalus, Chalcalburnus chalcoides mento, and Scardinius erythrophthalmus. During the starvation period all fish lost weight at about the same rate and the total amount of oxygen consumed during an experimental period of 20 h was about 40% lower in the starved than in the fed groups. Upon refeeding, both mass specific maintenance and routine rates of metabolism as well as relative growth rates increased rapidly, the peaks of these increases being directly proportional to the length of the starvation period. Maximum compensatory growth was observed after four weeks of starvation in C. chalcoides and S. erythrophthalmus, with relative growth rates reaching 30% d-1 during the first measuring interval after refeeding. The pattern of 'time-dependent compensatory growth' displayed by these fish is similar to the responses of a colonial hydroid in which the rate of catch-up growth increased with the amount of stress to which the animals had been exposed. The exact cost of compensatory growth cannot be calculated because oxygen consumption and growth were not measured simultaneously. However, on the basis of data and calculations reported by Wieser & Medgyesy (1990) it appears that compensatory growth, if fuelled by the metabolic power indicated by our measurements of oxygen consumption, would have to be about twice as efficient as normal growth in the related species Rutilus rutilus.