Produção de tambaqui (Colossoma macropomum) e pirapitinga (Piaractus brachypomus) em diferentes densidades de estocagem em RAS

Abstract

Stocking density is a crucial tool for commercial fish production, linked to the production potential of the fish production system and the health, welfare, and performance of the target species. In this context, this study aimed to evaluate juvenile fish production at different production stages of Colossoma macropomum and Piaractus brachypomus under different stocking densities in a recirculating water system (RAS). This study took into account the zootechnical performance, hematological and blood biochemical parameters, and somatic indices of C. macropomum and P. brachypomus, as well as the oxidative status, purinergic signaling, morphometry, carcass and fillet yield, and brachial morphometry of P. brachypomus. For C. macropomum, three experiments were conducted using juveniles with average initial weights of 0.54 g, 8.22 g, and 142.18 g, evaluated for 15 and 75 days at densities ranging from 0.3 to 6.0 kg m⁻³. The results indicated that, in the initial phases, stocking density did not compromise growth performance, although final biomass increased proportionally to density. For larger fish, higher densities impacted hematological and metabolic parameters, such as hemoglobin, glucose, and cholesterol, indicating physiological changes, but without significant growth impairment, demonstrating good adaptability of the species to intensive cultivation in RAS. For P. brachypomus, two initial experiments evaluated the effects of increasing densities (up to 7.90 kg m⁻³) on juveniles weighing between 1.5 g and 6.66 g for 20 days. The data showed that high densities reduced dissolved oxygen, creating a hypoxic environment, negatively affecting growth, weight gain, and hematological parameters such as hemoglobin and mean corpuscular volume. In subsequent experiments, juveniles weighing 29.55 g and 250 g were maintained for 90 days at densities of up to 4.5 kg m⁻³. During this period, growth performance, oxidative profile, enzyme activity, and gill morphometry were evaluated. Higher densities increased feed intake, biomass, and the activity of hepatic and muscle antioxidant enzymes (SOD, CAT, GST, GSH), in addition to inducing morphological changes in the gill lamellae. Purinergic signaling, assessed by NTPDase activity, was modulated by density, but without compromising productive performance. Overall, the results demonstrate that C. macropomum exhibits greater physiological tolerance to high densities in RAS from the initial stages, while P. brachypomus responds negatively to high densities in the early stages, performing better in later stages, even under metabolic challenges. The study reinforces the importance of defining specific stocking protocols for each phase of the production cycle and species, aiming to optimize production and ensure animal welfare. Long-term experiments that integrate all phases of cultivation are recommended to support sustainable and efficient practices for fish farming of native species in intensive systems.