Nárcia Carolina Santos da Silva

This study evaluated the effects of two rearing systems – recirculating aquaculture system (RAS) and biofloc technology (BFT) – as well as two stocking densities (3.75 and 7.5 kg m⁻ ³ ) on the performance, physiology, lipid profile, oxidative status and intestinal health of Piaractus brachypomus (70.75 ± 0.72 g, 15.87 ± 0.30 cm) over 60 days. BFT exhibited higher concentrations of dissolved oxygen, nitrite, nitrate, and alkalinity compared to RAS. The lower density (3.75 kg m⁻ ³ ) resulted in greater final weight and length, weight gain, daily gain, specific growth rate, and improved feed conversion, whereas the higher density (7.5 kg m⁻ ³ ) led to greater final biomass, feed intake and survival. Fish reared in RAS presented higher levels of plasma glucose, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, albumin, total proteins, and hepatic enzyme activities (alanine aminotransferase and aspartate aminotransferase), whereas fish reared in BFT showed higher erythrocyte counts, mean corpuscular hemoglobin concentration, triglycerides, very low-density cholesterol, and urea. Histologically, fish maintained in BFT displayed taller intestinal mucosal folds, whereas those in RAS showed better mucosal integrity and a higher density of goblet cells. No changes in fish oxidative status were detected among the evaluated systems or stocking densities. Furthermore, the stocking density of 3.75 kg m⁻ ³ favored greater hepatic lipid deposition. Taken together, the results indicate that P. brachypomus demonstrates high physiological and morphological plasticity, maintaining satisfactory productive performance in both intensive systems. Stocking density was the main modulating factor, with better growth and anabolic metabolism indices at the lowest density.

This study evaluated cherry tomato seedling production using pirapitinga RAS wastewater as the sole nutrient source in four substrate formulations: T1 (sand, gravel and coconut fiber), T2 (sand and gravel), T3 (gravel and coconut fiber), and T4 (sand and coconut fiber). No differences were observed for germination quality, germination percentage, seedling vigor index, germination vigor index, moisture content, total wet biomass, total dry biomass, or mortality. For small plants, leaf number (LN) was higher in T2 and lower in T4, while root length was greater in T3. The number of medium plants was higher in T3 and lower in T4; LN was higher in T1 and T2 and lowest in T3. For large plants, LN was higher in T1 and T2 and lower in T3; total length was higher in T1 and lower in T3 and T4. Visual differences in substrate water retention were observed: T4 exhibited rapid surface drying, T1 and T2 showed moderate moisture persistence, and T3 maintained surface water. Leaf yellowing was observed after 25 days, suggesting possible nutrient limitation or reduced nutrient availability at the measured pH. These findings indicate that substrate physical characteristics influence early seedling growth performance, whereas pirapitinga RAS wastewater can serve as a viable nutrient source.

Hesperozygis ringens essential oil (HREO), rich in pulegone and limonene, has potential application in aquaculture due to its beneficial properties. This study evaluated the effects of dietary supplementation with HREO (0.0, 0.75, 1.0, and 2.0 g HREO kg feed⁻¹) for 30 days on the physiological responses of Colossoma macropomum before and after a simulated 4 h transport. Fish were sampled at four time points: before transport (Basal), immediately after transport (IAT), and at 24 h (AT24) and 48 h (AT48) post-transport. Growth performance and survival (>96%) were not affected by HREO. Hemoglobin concentration, mean corpuscular hemoglobin concentration (MCHC), and intestinal coefficient showed significant responses to dietary HREO. After transport, survival was 100% for all treatments, and hematological and biochemical parameters varied according to dose and recovery time, with 2.0 g HREO kg feed⁻¹ showing the most consistent benefits, such as stabilization of hemoglobin, MCHC, and plasma proteins during recovery at AT₂₄ and AT₄₈. Water quality parameters did not differ between treatments at transportation end. These findings suggest that dietary HREO may contribute to enhance the physiological responses to transport in C. macropomum, supporting its potential use as a sustainable nutritional strategy.