This study evaluated the effects of dietary supplementation with citral on growth performance and intestinal parameters, and specific activity of the digestive enzymes of Sardinella brasiliensis. 240 juvenile S. brasiliensis were randomly distributed in a recirculating aquaculture system (RAS) composed of 12 circular tanks of 150 L (n = 20 per tank). A diet without citral addition (control) and three diets containing different levels of citral inclusion (0.5, 1.0 and 2.0 mL kg*feed–1) were used in the fish feeding management during 20 days. The indexes of zootechnical performance, survival, weight gain, specific growth rate, feed conversion and condition factor of the fish were verified, as well as digestive enzymes and histological analysis. A significant positive relationship was found between citral supplementation and fish survival. In the specific activity of digestive enzymes, dietary citral supplementation at 2.0 mL* kg feed–1 increased lipase and amylase activity. Citral supplementation positively influenced the number of villi and intestinal crypt depth. Furthermore, the inclusion of citral at 0.5 mL kg*feed–1 increased the intestine diameter of the fish. The results of the experiment suggest that the addition of citral as an additive in the diet of S. brasiliensis improved the survival of fish.

The aim of this study was to investigate the ideal density to use in transport operations for Brazilian sardines Sardinella brasiliensis (Steindachner, 1879). For this purpose, 4,020 juveniles S. brasiliensis (0.51 ± 0.10 g and 3.89 ± 0.32 cm) were randomly distributed in 60L-polyethylene bags filled with 20 L of water (salinity 35 g/kg) at densities of 15, 10, 5, 2.5 and 1 g∙L-1, all in triplicate. The transport bags were inflated with pure oxygen (about ⅔) and sealed with elastic bands. The duration of the simulated transport was 24 h. Then, survival rate, as well as analyses of water quality, was performed. The results showed that density had considerable influence on survival and water quality. At the density of 15 g∙L-1 dissolved oxygen reached 0.0 mg∙L-1, causing 100% mortality at the end of the experiment, while the density of 10 g∙L-1 showed a higher amount of N-NH3 in the water. Survival was the same at densities below 10 g∙L-1. Densities ≤ 10 g∙L-1 are recommended for the transport of S. brasiliensis lasting up to 24 h.

The use of residual biomass from industrial seaweed processing in aquafeeds may represent a potential route for the reuse of residual biomass within a circular-economy framework. This proof-of-concept trial evaluated the effects of dietary supplementation with wet solid residue from the seaweed Kappaphycus alvarezii in Mugil liza over 80 days under a mixed-feeding system. The treatments comprised nominal wet-residue levels corresponding to 0, 6, 12, 18, 24 and 30% of the reference daily feed intake, equivalent to 0, 0.7, 1.5, 2.2, 2.9 and 3.5% of the dietary mixture on a dry-matter basis, respectively. No mortality occurred, indicating no detectable adverse effects under the tested conditions. Haematological data indicated a pattern consistent with hormesis, with the 6% and 12% nominal wet-residue levels associated with increased erythropoietic responses. Intestinal integrity and fillet nutritional quality were preserved; however, eviscerated yield showed numerical variation among treatments, with the lowest median value observed at 18%. The mixed-feeding strategy allowed a reduction in commercial feed input without compromising growth. Overall, the tested nominal wet-residue levels, corresponding to 0.7–3.5% of the dietary mixture on a dry-matter basis, were not associated with detectable impairment of survival, intestinal integrity or fillet quality. Future studies should employ randomized designs with replicated experimental units to further explore the potential of using K. alvarezii processing residue as a partial replacement for traditional feed components in M. liza production.