Marcele Trajano de Araújo

Aim of study: To assess the performance of the giant freshwater prawn Macrobrachium rosenbergii (De Man, 1879) during the nursery phase under different culture systems (water exchange ‑ WES and biofloc ‑ BFS) and varying crude protein levels, using high‑density culture conditions (2,500 post‑larvae m‑³). Area of study: This study was conducted at the Federal Rural University of Pernambuco, in Brazil. Material and methods: The experimental design followed a 2 x 2 factorial arrangement, in which the initial variable corresponded to the type of rearing system, while the second one referred to the dietary crude protein content (35% and 40%), yielding in the combinations WES 35, WES 40, BFS 35, and BFS 40. Main results: The results demonstrated that the BFS 35 combination exhibited the lowest basic variable production cost and a substantial reduction in water footprint, ten times lower than the WES combinations. Furthermore, the BFS 35 system achieved a notable improvement in net benefits (2,876 USD 1000 m‑³), which was approximately twice that of the WES 35 (1,441 USD 1000 m⁻³) and nearly three times that of the WES 40 (1,006 USD 1000 m⁻³). Research highlights: The BFS 35 system can significantly reduce both the water footprint and the crude protein content in commercial feed, while simultaneously enhancing economic returns. These results suggest that the biofloc system with a 35% protein level is a viable and more sustainable option for the nursery phase of M. rosenbergii, offering a promising alternative to traditional systems.

The fact that the yellowtail tetra ( Astyanax lacustris ) exhibits sexual dimorphism in growth, with females typically outperforming males, has led to increased interest in sex control strategies for monosex production. This study aimed to refine a dietary masculinization protocol using 17α-methyltestosterone (MT) to induce phenotypic masculinization. Fish were fed diets containing 0, 10, 15, or 20 mg/kg MT for either 30 or 60 days, followed by rearing on a hormone-free diet until 212 days post-hatch. Sex ratio, growth performance, and gonadal traits were then evaluated. Treatment duration significantly influenced all assessed parameters at equivalent MT doses, whereas dose-dependent effects within the same exposure period were limited to body depth and gonadal weight. The 10 mg/kg MT treatment administered for 30 days yielded the highest masculinization efficiency, producing 83.3% phenotypic males. These results demonstrate that lower MT doses combined with shorter exposure periods can efficiently induce phenotypic masculinization in A. lacustris . This protocol provides a practical foundation for future studies aimed at evaluating the feasibility of neomale-based strategies for all-female production in freshwater aquaculture.

This study assessed the effects of dietary shrimp head meal (SHM) on growth performance, metabolism, antioxidant status, and health of Nile tilapia ( Oreochromis niloticus ) fingerlings. Five isonitrogenous and isoenergetic diets were precisely formulated on a digestible nutrient basis, containing graded SHM levels (0, 5, 10, 15, and 20%), and fed for 45 days to fish (3.24 ± 0.07 g) reared in 50 L tanks (10 fish tank ⁻¹ ; four replicates diet ⁻¹ ) within a recirculating aquaculture system. Growth performance increased significantly with SHM inclusion, and quadratic regression analyses suggested an estimated inclusion level near 16% associated with maximal weight gain and feed conversion efficiency. Improved eviscerated weight and whole-body protein, together with reduced hepatosomatic and viscerosomatic indexes and lipid content, indicated a shift toward lean growth and efficient nutrient utilization. Enhanced villus height and elevated digestive enzyme activities (amylase, proteases, and lipases) confirmed superior nutrient assimilation. Antioxidant defenses were strengthened by higher catalase and glutathione activities in liver and muscle, while feed malondialdehyde content decreased with increasing SHM levels during storage. Hematological and biochemical improvements, including higher erythrocyte, leukocyte, and platelet counts, elevated serum protein fractions, and lower glucose, cholesterol, alanine aminotransferase, and aspartate aminotransferase levels, reflected enhanced metabolic regulation, immune competence, and hepatoprotection. Collectively, these results demonstrate that SHM functions not only as a sustainable protein source but also as a functional feed ingredient that enhances physiological resilience. The valorization of shrimp-processing residues through SHM inclusion supports circular bioeconomic development and sustainable intensification in aquaculture.

Aquaculture plays a critical role in food security, with Nile tilapia (Oreochromis niloticus) being one of the most widely farmed species due to its resilience and adaptability. However, the reliance on traditional feed ingredients poses sustainability challenges. This study aimed to investigate the immunomodulatory effects of incorporating shrimp cephalothorax lipid extract (SCLE) and shrimp cephalothorax meal (SCM) in Nile tilapia diets as sustainable feed alternatives. Two experiments were conducted using diets with varying levels of SCLE (0.4%, 0.8%, 1.2%, and 1.6%) and SCM (5%, 10%, 15%, and 20%). A total of 200 healthy, uniformly sized Nile tilapia fingerlings were selected for two trials with average weights of 4.38±0.13 g and 3.24±0.07 g, respectively. Fish were distributed across 20 tanks and fed ad libitum for 45 days. Hematological parameters were analyzed, revealing that diets with SCLE significantly increased leukocyte, thrombocyte, and hematocrit levels, particularly at 1.6% inclusion. SCM inclusion also led to higher leukocyte counts, especially at 20%. These findings suggest that SCLE and SCM positively impact the innate immune system of Nile tilapia, enhancing their ability to resist pathogens. Additionally, the use of shrimp by-products in aquafeeds presents a viable strategy for reducing environmental waste and promoting more sustainable practices in aquaculture.