Produtive performance of Pseudoplatystoma corruscans (Spix & Agassiz, 1829) in two rearing systems: intensive and semi-intensive

Abstract

The objective of this study was to analyze the zootechnical performance of Pseudoplatystoma corruscans juvenile, reared in intensive (2.25 m³ net-cages í  NC- with 20 mm mesh) and semi-intensive (600 m² earthen ponds - EP) systems, with three treatments and nine repetitions, in the Vale do Ribeira, in the town of Pariquera-Açu, Sao Paulo, Brazil, between October 2002 to July 2003: Treatment 1 (T1) = 67 fish/m³, a total of 451 fish/pond í three net-cages placed in a pond (EP); Treatment 2 (T2) = 133 fish/m³, a total of 900 fish/pond í  three net-cages placed in a pond (EP); Treatment 3 (T3) = 0.75 fish/m², a total of 450 fish/pond. Each net-cage (treatments T1 and T2), and each pond (treatment T3) was regarded as a repetition. The fish, with initial mean weight and length of 73.82 g and 23.21 cm for T1; 72.96 g and 23.10 cm for T2, and 73.14 g and 22.99 cm for T3 were fed daily extruded feed (40% crude protein). The fishes received three servings of the ration of 4.0 mm of diameter in the Phase I (60 days), 5 to 10% of the live weight, and in the Phases II (120 days, 6.0 mm) and III (93 days, 8.0 mm), the fish were fed in two servings, the quantity ranging from 5-3% and 3-1% in Phases II and III. At the end of the studied period, the fish presented the following mean values: final mean weight and length: 712.49 g and 45.10 cm for T1; 852.13 g and 46.33 cm for T2; 1,179.17 g and 53.72 cm for T3. Daily mean weight gain: 2.34 g for T1; 2.85 g for T2, and 4.05 g for T3. Final total biomass: 223.01 g for T1; 541.10 g for T2, and 384.40 g for T3. Apparent feed conversion: 5.2:1.0 for T01; 5.0:1.0 for T02; 4.6:1.0 for T03. Survival rate: 69.55% for T1; 70.56% for T2; 72.44% for T3. Relative condition factor: 1.01 for T1 and T2, and 1.00 for T3. The T3 were significantly different from the other treatments (Pâ"°¥0.001). The physical and chemical parameters analyzed were within the acceptable standards for the species. The results of this study, under the conditions on that it has been carried out, indicate that P. corruscans exhibited higher productivity when reared in earthen ponds