To understand the impacts of salinity stress on the antioxidation of yellowfin tuna Thunnus albacares, 72 fishes (646.52 ± 66.32 g) were randomly divided into two treatments (32‰ and 29‰) and sampled at four time points (0 h, 12 h, 24 h, and 48 h). The salinity of the control group (32‰) was based on natural filtered seawater and the salinity of the stress group (29‰) was reduced by adding tap water with 24 h aeration to the natural filtered seawater. The superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) from liver, gill, and muscle tissues were used as the antioxidant indexes in this study. The results showed that the changes of SOD and GSH-Px in the gills were first not significantly different from the control group (p > 0.05) and finally significantly higher than the control group (SOD: 50.57%, GSH-Px: 195.95%, p < 0.05). SOD activity in fish liver was not significantly changed from 0 h to 48 h (p > 0.05), and was not significantly different between the stress group and control group (p > 0.05). With the increase in stress time, GSH-Px and MDA activities in the liver of juvenile yellowfin tuna increased first (GSH-Px: 113.42%, MDA: 137.45%) and then reduced (GSH-Px: −62.37%, MDA: −16.90%) to levels similar to the control group. The SOD activity in the white and red muscle of juvenile yellowfin tuna first decreased (white muscle: −27.51%, red muscle: −15.52%) and then increased (white muscle: 7.30%, red muscle: 3.70%) to the level of the control group. The activities of GSH-Px and MDA in white and red muscle increased first (white muscle GSH-Px: 81.96%, red muscle GSH-Px: 233.08%, white muscle MDA: 26.89%, red muscle MDA: 64.68%) and then decreased (white muscle GSH-Px: −48.03%, red muscle GSH-Px: −28.94%, white muscle MDA: −15.93%, red muscle MDA: −28.67%) to the level observed in the control group. The results from the present study indicate that low salinity may lead to changes in the antioxidant function of yellowfin tuna juveniles. In contrast, yellowfin tuna juveniles have strong adaptability to the salinity of 29‰. However, excessive stress may consume the body’s reserves and reduce the body’s resistance.

This study was conducted to determine whether curcumin has a positive effect in greater amberjack (Seriola dumerili), especially the ammonia nitrogen stress tolerance ability. The results showed that the stress recovery process of digestive enzymes amylase and trypsin, as well as absorptive enzymes Na⁺/K⁺-ATPase, γ-GT and CK, was accelerated. Lysozyme activity increased in the fish fortified with both curcumin diets. Aspartate aminotransferase activity restriction was activated at a low curcumin level. However, alanine aminotransferase activity restriction happened only at 0.02% dietary curcumin. Facilitation of lipid metabolism by curcumin was very clear, as triglyceride and total cholesterol content was basically maintained at the original level or even showed a slight decrease after recovery. HSP70 and HSP90 genes were not evidently stimulated to express in liver, kidney and spleen tissues. In addition, curcumin showed its inhibition capacity on IL1β and IFN-γ and a promoting effect on TGF-β1. The expression of NF-κB1 decreased in a higher degree in fish fed with 0.02% dietary curcumin, while 0.01% dietary curcumin accelerated the recovery pace of C3 and lgT after stress. This study showed that dietary curcumin supplementation can enhance ammonia nitrogen stress tolerance in greater amberjack, and its application prospect can be confirmed.

In this study, we investigated the effect of dietary curcumin on non-specific immune responses and antioxidative ability in Seriola dumerili under ammonia stress and post-recovery. Three diets were prepared to contain 0, 75, and 150 mg/kg of curcumin. A total of 225 greater amberjack (initial weight: 100.90 ± 0.03 g) were distributed into nine cylindrical tanks, constituting an experimental design with three treatments and three replicates. After 56 days of feeding, plasma, intestinal, and hepatic enzyme activities were evaluated. Then, an acute ammonia challenge experiment was conducted. Ten fish per tank were subjected to acute ammonia stress (total ammonia-N: 1000 mg/L) for eight minutes followed by six minutes of recovery. The results indicated that dietary curcumin significantly promoted intestinal and hepatic alkaline phosphatase (ALP) and acid phosphatase (ACP) levels as well as hepatic antioxidative enzymes such as superoxide dismutase (SOD), total antioxidant capacity (T-AOC), reduced glutathione (GSH), and glutathione peroxidase (GSH-Px) of greater amberjack. In addition, curcumin addition improved the activities of antioxidant enzymes, such as SOD, T-AOC, GSH, GSH-Px, and catalase (CAT), and reduced malondialdehyde (MDA) content in liver, spleen, head kidney, and brain tissues after post-recovery. The indexes related to immunity and antioxidant enzymes in the liver, gill, and spleen rose again to some extent, but they showed the worst recovery ability in the head kidney and brain tissue samples. These results indicate that dietary curcumin supplementation could increase non-specific immune responses, antioxidant ability, and enhance resistance to high ammonia stress in juvenile S. dumerili.

In this study, we sought to characterize the effect of water vibration frequency stress on crimson snapper (Lutjanus erythropterus) survival to determine an optimal transportation speed. To achieve this, we used a transport tank (25 cm × 17 cm × 16 cm) to simulate the transport process. After 8 h at five different vibration frequencies (D1 = 75 rpm, D2 = 105 rpm, D3 = 135 rpm, D4 = 165 rpm, and D5 = 195 rpm), the pH and dissolved oxygen (DO) levels in the tanks decreased; ammonia nitrogen levels (NH₄-N) and temperature (T) increased with increasing density; and significant changes in oxidative stress biomarkers, digestive enzymes, and ATPase levels were observed in crimson snapper fry. The enzyme activity increased and reached the maximum value at 195 rpm. The experimental results suggested that during the actual transport, when using transport tanks, the length of the transport time was less than 8 h, and setting the vibration frequency for transportation at 135 rpm was more appropriate, that is, a speed of 50 km/h for transporting crimson snapper fry.

The Asian seabass (Lates calcarifer) has high economic value and is the primary aquaculture species in China. Licorice (Glycyrrhiza uralensis) as a feed additive has demonstrated significant immunological benefits in aquaculture. However, its effects on the growth of aquatic animals are largely unexplored. This study explored the influence of licorice on the level of growth-related genes in Asian seabass by conducting an experiment using artificial feed with 0%, 1%, 3%, and 5% licorice. The impact on growth performance and the expression of several genes, including growth hormone–releasing hormone (GHRH), growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor 1 (IGF1), IGF2, IGF2 receptor (IGF2R), myostatin 1 (MSTN1), and myostatin 2 (MSTN2), were studied over 56 d. According to the results, the 3% and 5% licorice-supplemented diets significantly improved survival rates and weight gain compared to the control group. Licorice affected the level of growth-associated genes in Asian seabass and significantly increased the levels of GHR and IGF1 in the liver. However, a 5% licorice diet downregulated the expression of IGF2. As the licorice content in the diet increased, the levels of IGF2R and MSTN1 in the muscle tissue first decreased and then increased, and licorice addition inhibited the MSTN2 expression. The inclusion of licorice in the feed led to a significant downregulation of the GH and GHRH expression (p < 0.05). In summary, adding a certain proportion of licorice to the diet can improve the survival rate of the Asian seabass. Moreover, a proper proportion of licorice can increase the expression of related growth genes of fish, effectively increasing their weight gain rate and specific growth rate.

To optimize juvenile barramundi (Lates calcarifer) feeding strategies, this study compared cannibalism (CB), formulated feed (FF), and mixed feed (MIX: formulated + biological feed) on growth, physiology, and immune-related gene expression. 36-day-old juveniles (initial body weight) were randomized into 3 groups (1 Lates calcarifer was placed in each tank, with 15 replicates in each group.) for a 20-day trial. Growth performance: MIX group showed significantly higher weight gain rate (862.31 ± 346.66) and specific growth rate (93.2 ± 42.48) than FF and CB groups (P < 0.05); CB group outperformed FF (P< 0.05). Physiology: MIX had the highest alkaline phosphatase (AKP) and pyruvate kinase (PK) activities (P < 0.05), and significantly elevated alanine aminotransferase (ALT) activity, lipid peroxide (LPO) content, but the lowest catalase (CAT) activity (P < 0.05). Gene expression: CB group had the highest lysosomal protease (cts1a) and glycolytic gene (eno3) levels (P < 0.05); FF group showed higher heat-shock protein 90(hsp90) and pro-inflammatory cytokine (IL1β) expression (P < 0.05). FF exhibited the highest SOD activity and IL1β levels (P < 0.05), indicating strong antioxidant. Conclusion: MIX promotes growth but risks liver damage/oxidative stress; CB serves as emergency nutrition but requires management to avoid; FF exhibits significant antioxidant advantages despite poor growth performance. "Mixed feeding + immune enhancers" is recommended for industrial seedling production to balance growth and health.