Compensatory growth in gilthead sea bream ( Sparus aurata) compensates weight, but not length

Abstract

We conducted a 60-day experiment to investigate whether compensatory growth can fully compensate for reduced growth during food deprivation, and whether food deprivation improves feed conversion ratio ( F CR) in gilthead sea bream (Sparus aurata L). During the first half of the experiment, four groups of fish were subjected to feeding levels ranging from starvation to satiation. All groups were fed to satiation during the second half of the experiment. As expected, the three food-deprived groups showed smaller growth rates during the first half, and compensatory growth in weight during the second half of the experiment. Although this may suggest complete compensation is possible, our analysis of length data suggests otherwise. The analysis shows that von Bertalanffy growth rates in length during the second half of the experiment did not differ significantly among groups. This leads us to conclude that fish did not compensate growth in length, and that the observed compensatory growth is mainly due to the rapid increase in condition of the fish. Because the maximum condition for any given length is limited, length limits the maximum weight of each fish. It follows that any retardation of growth in length implies a permanent loss of the weight increase potential which we defined as the maximum attainable increase in weight in a given period. Therefore, our results suggest that reduction in feeding which reduces growth also permanently reduces maximum attainable weight of gilthead sea bream in any given period. Considering the theoretical background we argue that, in addition to weight, one should always analyze length (or some other measure that incorporates length, such as condition) when characterizing compensatory growth. Finally, to facilitate comparison of our experiments to previous work in the field, we estimate gilthead sea bream maintenance ratio at 0.3% of body weight per day, and the optimum feeding ratio at 1.06% of body weight per day based on specific growth rate.