The effects of feeding rate and feeding frequency on the growth of laboratory-reared common snook (Centropomus undecimalis) were evaluated. Juveniles with mean±SD weight of 2.55±0.48 g and total length of 6.81±0.48 cm were divided into groups of 20 fish and reared in 30 polyethylene tanks of 50 L for 60 days. The experimental design was a 3 × 3 factorial with three feeding frequencies (F2, F4, and F6: two, four, and six daily meals, respectively), three feeding rates (R1, R2.5, and R4: 1.0, 2.5, and 4.0%/day of fish biomass, respectively), and three replicates, totaling nine treatments (F2R1, F2R2.5, F2R4; F4R1, F4R2.5, F4R4; F6R1, F6R2.5, and F6R4). The external control consisted of four meals a day offered to apparent satiety (F4S). Every 15 days, weight and length of all fish were measured to adjust the amount of feed offered. Water quality variables remained within adequate levels for this species. Feeding rate had a greater influence on performance than frequency. Survival, condition factor, and the initial and final coefficients of weight variation had no significant effect among treatments. Feeding frequency and rate directly influenced length and weight gains, feed efficiency, specific growth rate, and apparent feed conversion rate. For common snook juveniles weighing between 1 and 16 g, it is recommended to offer four to six daily meals at a feeding rate between 3.31 and 1.86% per day, which should decrease according to fish size.

Infectious myonecrosis virus (IMNV) is considered one of the pathogens that most affect the production of Penaeus vannamei , causing economic losses estimated at billions of dollars. P. vannamei rearing is expanding to inland waters, which are commonly used for the farming of Macrobrachium rosenbergii , increasing the probability of exposure of this freshwater prawn to viruses often reported in penaeids, including IMNV. Therefore, the aim of the present study was to investigate the susceptibility of M. rosenbergii to IMNV through an intramuscular challenge. M. rosenbergii subadults and adults were inoculated intramuscularly with IMNV obtained from the abdominal muscle tissue of naturally infected P. vannamei . The viral challenge lasted 21 days. All samples had positive nested-PCR results as well as clinical signs and histopathological findings typical of the virus, such as hemocyte infiltration and muscle sinus dilation. This is the first study to demonstrate the susceptibility of M. rosenbergii subadults and adults to IMNV. Although no massive mortalities were detected in the challenged prawns, the presence of M. rosenbergii as a viral source in the cultivation environment should not be underestimated.

The use of functional feeds in aquaculture has increased due to the reduction in fishmeal and the need to improve the gut health of farmed organisms. This study evaluated the effects of supplementing nucleotides (NT) and mannan oligosaccharide (MOS) in the diet of juvenile Penaeus vannamei reared in a synbiotic system for 60 days. Four treatments were tested: a control diet without additives (RC); a diet supplemented with 2 g NT kg⁻¹ (NT); a diet supplemented with 2 g MOS kg⁻¹ (MOS); and a diet supplemented with 1 g NT kg⁻¹ and 1 g MOS kg⁻¹ (NT/MOS). Water quality, zootechnical performance, gut morphology, microbiota indicators, and economic benefits were evaluated. There were no significant differences in water quality or production performance among treatments. However, additive supplementation improved economic efficiency and net revenue, with the NT/MOS treatment showing a 7.06% economic gain relative to the control. MOS supplementation increased the proportion of Bacillus spp. to 13.9 × 10⁷ CFU g⁻¹, suggesting a prebiotic effect and potential control of Vibrio spp. Morphologically, supplemented shrimp exhibited shorter mucosal folds and thicker gut walls. NT and MOS supplementation appeared to be an economically promising strategy for shrimp production in synbiotic systems.