Effects of successive size grading on the growth of juvenile European sea bass (Dicentrarchus labrax L.) at three temperatures

Abstract

Juvenile European sea bass from the same fish stock were selected by successive size grading processes using 2, 3 and 4 mm bar graders at 79, 96 and 99 days post hatching, thus forming three groups (n=300) consisting of similar-sized fish that differed by time of each group formation. The growth patterns of fish groups were studied at three temperatures during 5 weeks of rearing. Three-way anova followed by the Tukey multiple comparison test (P<0.05) showed a high dependence of growth on the temperature applied. The smallest size and weight of fish were detected in all groups reared at 19 °C compared with fish held at 21 and 23 °C respectively. Differences in coefficients of variation of lengths were small and insignificant between groups and temperatures. Growth in the length of sea bass juveniles during the test period was a linear function of time and no differences were observed in growth rate among groups at a particular temperature. Growth rates of fish were 0.71 ± 0.02, 0.62 ± 0.01 and 0.52 ± 0.02 mm day−1 at 23, 21 and 19 °C respectively. These results indicated that the variations in body size of juveniles in the test period were not the result of differences in the growth potential of individuals.