Influence of the stocking density on the growth, feeding, survival rate and muscle cellularity of juvenile specimens of common name shi drum, Umbrina cirrosa L.

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Umbrina cirrosa specimens (mean weight 9.5 g, mean length 9 cm) were categorized in three densities (4, 9 and 15 kg/m3) in order to study the influence of stocking density on the growth, survival and feed conversion rates. The body and muscle parameters were studied at 0, 43 and 84 days of the experiment. After 43 days, the highest body parameters values (body length and weight) were found in specimens reared at 9 kg/m3, followed by the specimens reared at 4 kg/m3, showing the specimens reared at 15 kg/m3 the lowest growth. These results showed a negative effect of the high density on the growth, being the intermediate density (9 kg/m3) the most favorable density for the growth at this stage. Muscle cellularity was different among the groups, being the hypertrophy values higher at high density of rearing (15 kg/m3) than at 4 and 9 kg/m3. In contrast, the hyperplasia was higher at 4 kg/m3 than in the rest of densities. The group reared at 9 kg/m3 showed intermediate values of hypertrophy and hyperplasia. At 84 days of the experiment, the muscle cellularity was similar at 4 and 9 kg/m3, thus indicating a compensatory hypertrophic growth at 4 kg/m3. The highest values of body weight were reached at 9 kg/m3. Moreover, the feed conversion rates and the percentage of survival were better at 9 than at 4 kg/m3.