Growth, survival and bone alterations in <italic>Piaractus mesopotamicus</italic> larvae under different rearing protocols

Abstract

<p>The pacu (<bold>Piaractus mesopotamicus</bold>) is a neotropical freshwater fish. It is one of the most important species farmed in areas of the Parana and Paraguay Rivers basins. The effects of different rearing protocols on growth, survival and incidence of skeletal malformations in pacu larvae were analyzed. A total of six experimental treatments were considered, consisting of: a semi-intensive larviculture (L<sub>S</sub>) in ponds; intensive larviculture (L<sub>In</sub>) in laboratory (both L<sub>S</sub> and L<sub>In</sub> until 60 days of life); and mixed larviculture, with 20 days of semi-intensive larviculture into cages in ponds after 14 (L<sub>1</sub>), 21 (L<sub>2</sub>), 33 (L<sub>3</sub>) or 40 (L<sub>4</sub>) days of laboratory larviculture. At the end of the experimental period, L<sub>S</sub>larvae showed higher growth rate, with average weight values (2.28g) and total length (TL-48.20mm) statistically higher than the rest (P<0.05). L<sub>1</sub> to L<sub>4</sub> treatments showed intermediate growth values, without differences between them (P>0.05), while L<sub>In</sub> presented the lowest growth (P<0.05). Survival was around 75% in all experimental groups, except L<sub>S</sub>, that presented a significantly lower value (17.5%, P<0.05). Skeletal abnormalities were detected in all experimental treatments, but L<sub>In</sub> and L<sub>1</sub> presented the lowest incidence. In no case, visible morphological alterations were found. This study shows that prolonging pacu rearing under laboratory conditions at high densities improves temporal availability and survival of juvenile without affecting growth or subsequent osteological development of fish.</p>