The growth curve is a tool that can be used to determine the performance potential of fish at different ages. The aim of this study was to evaluate the growth curve of pacu (P. mesopotamicus) and the patinga hybrid (P. mesopotamicus × P. brachypomus) cultivated in a semi-intensive system. In the initial phase of the experiment, the pacu and patinga fish weighed 32.6 ± 7.5 g and 24.9 ± 7.1 g, respectively. The Gompertz model was adopted to describe the growth curve. At the end of the experiment, body weight, standard length, head length, body height and body width did not differ significantly between the pacu (625.9 g; 25.6 cm; 7.2 cm; 12.1 cm; 4.5 cm) and the patinga hybrid (727.1 g; 27.3 cm; 7.6 cm; 13.2 cm; 4.9 cm). The asymptotic value (parameter A), relative growth rate (parameter B), and age at the inflection point (parameter C) of the growth curve of the two species were similar for weight and for the evaluated morphometric traits. The asymptotic values obtained for weight in the pacu and the patinga hybrid were 1212.0 g and 1348.0 g, respectively. The growth curve of the patinga hybrid is similar to that of pacu, contrasting with the belief of many fish farmers
This study was carried out to determine the toxicity and biochemical and morphophysiological changes caused by Serjania erecta leaf aqueous extract in pacu (Piaractus mesopotamicus). For acute toxicity testing (CL 50-4h ), pacu juveniles were exposed during 4 h to Serjania erecta aqueous extract concentrations of 2.5, 12.5, 25, 50, 100, and 150 µg mL -1 , which were added directly to the water in the tanks. In the control group, the animals were kept in water free from aqueous extract. CL 50-4 h was estimated at 57.43 µg mL -1 . After exposure to the aqueous extract, the highest (P<0.05) glucose concentration and the lowest (P<0.05) plasma sodium level were when the fi sh were exposed to the S. erecta concentration of 50 µg mL -1 . Mortality occurred at S. erecta extract levels higher than 50 μg mL -1 , and all fi sh died at concentrations greater than 100 μg mL -1 . In addition, exposure to this extract caused severe histological changes in the gills and liver with higher prevalence of necrosis (30.2%), and fatty degeneration (77.4%) respectively. At the concentrations tested here, S. erecta aqueous extract causes morphofunctional alterations in this fi sh species.
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