Densidade de estocagem na larvicultura e engorda do tambaqui colossoma macropomum em sistema de recirculação de água (sra)

Abstract

The aim of the present study was to evaluate the effects of stocking densities on larviculture and fattening of Colossoma macropomum in RAS. For this, 3 experiments were carried out. In the first, the growth, survival and heterogeneity of the batch during larviculture of C. macropomum submitted to densities of 10 (D10), 30 (D30) and 50 (D50) L-1 larvae with five replications were evaluated. The larvae were fed with Artemia nauplii during the first 15 days and with a commercial diet from day 16 to day 30 of cultivation. At the end of 30 days of larviculture, survival, weight, length and specific growth rate were not affected by stocking densities (P<0.05). Heterogeneity in all tested densities showed a predominance of Medium (M) class animals (>18.0 mm and <22.2 mm) (P<0.05). The second experiment investigated the densities of 60 (D60), 120 (D120) and 180 (D180) L-1 larvae, with four replicates, evaluating the growth, survival and heterogeneity of the batch and including an economic analysis, using the same managements of the first experiment. At the end of 25 days of larviculture, ammonia was affected by stocking density with the highest value for D180, however performance and survival were not affected by densities (P>0.05). The number of animals produced at the end of larviculture increased with the increase in stocking density (P<0.05), with a predominance of class M (>17.0 mm and < 22 mm; >0.07 g and < 0.13 g) at D60 and D120, while there was no difference between P (17.0 mm and < 0.07 g) and M at D180 (P > 0.05). The net income was negative for the D60 treatment, while for D180 it had the best net income. In the third experiment, the effects of stocking density and classification of animals by size on the growth and physiological parameters of juveniles of C. macropomum in RAS were evaluated. This experiment was divided into three phases. In Phase I, juveniles (34.88 ± 0.60g) were stocked at densities of D0.5= 0.5; D1.0= 1.0 and D1.6= 1.6 kg m-3 for 53 days. In Phase II, juveniles (150.61 ± 0.58 g) were stocked at densities of D1.5 = 1.5, D3.0 = 3.0 and D4.5 = 4.5 kg m-3 for 60 days. In Phase III, animals were classified according to weight (or mass) in P = 300–400g; M = 400–500g and G = >500g for 60 days with initial biomass of 3.9 kg m³ for each class. In all phases of the experiments, the animals were fed twice a day (08:00 and 16:00), until apparent satiation with commercial feed. After the first 30 days of Phase I, final weight (FW) and daily weight gain (DWG) were higher for D0.5, but feed conversion ratio (FCR) was lower (P<0.05). Daily feed intake (DC) was the lowest for D1.6 and the highest for D0.5 (P<0.05). At 53 days, FW, DC and DWG were higher for D0.5 and lower for D1.6. From day 31 to day 53, there was a decrease in hemoglobin (Hg) and hematocrit (Htc) and an increase in the hepatosomatic index (HSI) to D0.5 (P<0.05). After the first 30 days of Phase II, FW, DWG and DC were higher for D1.5 (P<0.05). After 60 days, D1.5 showed the highest values of FW and HSI and the lowest values of glucose, triglycerides and Htc (P<0.05). In Phase III, after 30 days FW, DWG and DC were higher for class G (P<0.05), and FW remained higher for class G after 60 days. The HSI was higher for class P and lower for class G (P<0.05), while triglycerides, cholesterol, total proteins and Hg were lower for classes P and M (P<0.05). With the results obtained by this research, we conclude that the larviculture of C. macropomum can be carried out in RAS with up to 180 larvae L-1 with good performance and survival results. In addition, good indicators of economic and financial viability were verified for densities greater than 120 larvae L-1. Complementary studies should be carried out to optimize management in this production phase, such as classification to produce more homogeneous batches of C. macropomum. In the fattening phase, the stocking density must be evaluated according to the size of the animals and, despite the better performance found for lower densities (phases I and II), higher densities produced greater biomass. The classification of animals is an important management strategy to maintain uniformity for commercialization.