To sustain normal development, high survival, and rapid growth, marine fish larvae require a diet rich in polyunsaturated fatty acids, which could decrease the risk of reactive oxygen species accumulations. Consequently, a 60-day feeding experiment was conducted to determine the effect of silymarin (SM) supplementation in weaning diets on the growth performance, survival, antioxidant enzyme activities, and fatty acids profile of European seabass ( Dicentrarchus labrax ) larvae. Four isonitrogenous and isolipidic diets were investigated using SM at levels of 0, 200, 400, and 600 mg kg ⁻¹ (SM _0.00 , SM ₂₀₀ , SM ₄₀₀ , and SM ₆₀₀ , respectively). The findings showed that, in a dose-dependent manner, increasing dietary levels of SM enhanced survival, growth, and feed utilization. In the SM ₆₀₀ group, the weight gain, survival, and feed conversion ratio (FCR) improved by 123.21, 11.66, and 38.72%, respectively, compared to the control group. The dose-response analysis demonstrated a strong positive correlation (R2=0.96) between SM levels and weight increase, and a strong negative correlation (R2=0.88) between SM levels and FCR. The antioxidant enzyme activities of larvae given SM-enriched diets were significantly greater than those of the control group. Compared to the control group, the CAT and SOD improved by 81.77 and 5.08% in the SM600 group. In addition, the saturated fatty acid content decreased while the unsaturated fatty acid content increased, particularly in the SM600 group. The results indicate that supplementing the micro diet of European seabass larvae during weaning with SM at a dose of 600 mg kg ⁻¹ increases growth, survival, antioxidant status, and fatty acid profiles.

Freshwater scarcity poses challenges to aquaculture worldwide, including countries like Egypt. In this study, we investigate the feasibility of integrating underground saline water (USW) with varying salinities into a Biofloc (BFT) system for desert mariculture of Florida red tilapia (FRT) and its impacts on water quality, fish performance and health. Four BFT treatments (C/N ratio = 15) were examined in triplicate using four salinity levels 0 ppt, 12 ppt, 24 ppt and 36 ppt, expressed as S0, S12, S24 and S36, respectively. For 75 days, a total of 12 fiberglass tanks (each 250 L⁻¹ water) were used to store FRT fry (average weight of 1.73 ± 0.01 g/fish). The fish were fed an experimental diet (protein/fat = 30/5) and an additional carbon source of rice bran. The results revealed that group S12 showed better growth indicators, higher survival rate, lower FCR, and lower ammonia levels, while group S0 exhibited lower growth indicators (final weight, weight gain, and specific growth rate) than all groups. The serum kidney, liver, and antioxidant indices performed better in the S12 group. At 12 ppt, the immune-related parameter (IgM) increased by 22.5%, while the stress parameter (cortisol) decreased by 40.8% compared to the S0 group. The liver and intestinal histopathological results revealed that the S12 and S24 groups performed better. Pathogenic bacterial load counts favored the S24 group, which had the lowest number among the groups studied. The recommended salinity for FRT cultivation in USW and BFT is 19.94-20 ppt, determined by polynomial regression of FW and FCR.

A 120-day growth trial was completed to assess rearing water quality and fish performance in terms of growth, feed efficacy, digestive enzymes, immunity, and antioxidant activity of seabass fed an experimental diet (ED) supplemented with commercial wood charcoal (WC) and activated wood charcoal (AC). Three levels (0, 10, and 20g) of WC and AC were administered, representing five treatments: control (CD) fish-fed ED without additives, (WC-1) fish-fed ED containing 10g kg⁻¹ WC, (WC-2) fish-fed ED containing 20g kg⁻¹ WC, (AC-1) fish-fed ED containing 10g kg⁻¹ AC, and (AC-2) fish-fed ED containing 20g kg⁻¹ AC. Three hundred fish (60.120.20g/fish) were stocked in 15 cement tanks (4.0m2.0m1.2m, water volume 5m³ each) at 20 fish/tank and a daily feed ration of 3 of body weight. Results revealed significant improvements with increased growth variables (final weight, weight gain, and specific growth rate), decreased FCR, and decreased ammonia levels and heavy metals (Cu, Cd, Fe, Mn, and Zn) content in rearing water, muscle, and liver with fish fed WC and AC supplemented diets. Furthermore, considerable improvements in digestive enzymes, immunity, and antioxidant activity, with enhanced kidneys, liver, intestines, gills, and spleen. Fish fed the WC-1 diet had a higher final weight (171.90g), better FCR (1.25), and improved internal organs than the other groups.