In this study, the effects of a mixed algal blend (Chlorella vulgaris, Euglena viridis, and Spirulina platensis) at different levels were evaluated on growth, hematological immune responses, and expression of immune genes in Labeo rohita against post-challenges of Aeromonas hydrophila. Fish samples were fed a diet containing different levels of mixed blend algal (0, 0.01, 0.02, 0.04 and 0.08% of basal diet). At the end of the feeding period, the fish were challenged with A. hydrophila and fish mortality was recorded over a 14-days period. To evaluate the serum biochemical (albumin, globulin), hematological parameters (Hb, RBC and WBC) and immune parameters (neutrophil activity, lysozyme activity, myeloperoxidase activity, antiprotease activity, ceruloplasmin activity, and bactericidal activity), as well as the expression of immune genes (NKEF-B, Lysozyme C and G, TNF α, TLR22, β2M, and β-actin), fish were sampled on Day 7, 14, 21 and 28. Fish were challenged with virulent A. hydrophila 30 days post-feeding and mortalities were recorded over 30 days post-infection. Results demonstrate that fish fed with a mixed algal blend showed that total body weight gain, specific growth rate, total serum protein, globulin, total hemoglobin content, white blood cells, neutrophil, lysozyme, bactericidal, myeloperoxidase, and antiprotease activity in dietary algae blended application was higher than in the control (p < 0.05). According to the results, relative expression of target genes showed significant increases of 0.02 to 0.04% in the treatment group compared to the control group (p < 0.05). At the end of the 30-day exposure to A. hydrophila, the fish that received the mixed algal blend had a significantly higher rate of survival than the control group, with the highest survival rate recorded in the 0.02% mixed algal blend (p < 0.05). According to the effective results of the mixed algal blend on stimulating the immune system and increasing fish resistance to A. hydrophila, it is recommended to use 0.02 to 0.04% of this mixed algal blend in rohu, L. rohita diets.

The current study focused on assessing the outcome of methanol extract of Chaetomorpha antennina (MECA) on the growth performance and immune modulation in both specific and non-specific immune responses through the assessment of neutrophil, serum lysozyme, serum myeloperoxidase, antiprotease, ceruloplasmin, reactive oxygen species (ROS), and reactive nitrogen species (RNS) activity in Labeo rohita (rohu) at 28 days post treatment along with assessment of the disease resistance capacity against Edwardsiella tarda at 30days post immunization. Fishes (n = 144; average weight 50.0 ± 0.23 g) were evenly divided into four treatments, with 12 fishes per tank in triplicates. The MECA was injected intraperitoneally in the fishes at different doses as 0, 25, 75, and 150 mg/kg of the body weight. The results demonstrated that fish treated with MECA have an increased body weight, specific growth rate, and feed conversion ratio (p < 0.05) with respect to the control group. Results suggested that the MECA inclusion can significantly enhance (p < 0.05) the levels of serum lysozyme, neutrophil function, serum antiprotease activity, cellular RNS, and ROS production. Exposure to MECA of 75 mg/kg showed a significantly higher survival percentage against E. tarda disease infection. These results indicate MECA as a stimulant of immunity in L. rohita against E. tarda. The results suggested that MECA is a potent immunostimulant in finfish aquaculture and can offer higher economic welfare.

Cadmium (Cd) is a non-essential element with sub-lethal effects even at low concentrations. The persistent nature of Cd and its tendency to bioaccumulate eventually create harmful effects on water biota, including fish. Cd affects various aspects of hormonal action in fish since it bioaccumulates in the endocrine system and hinders the synthesis, secretion, and metabolic activity of hormones, causing severe damage along the hypothalamus–pituitary–gonadal axis. Linking reproductive and developmental impairments in fish with ecologically relevant concentrations of individual metals can be challenging due to the complexity of aquatic ecosystems. This review deliberated the significant and novel trends of toxicological difficulties and approaches, including elucidating environmental sources’ bioavailability and Cd-induced toxic effects in freshwater fish. Both acute and chronic exposure to Cd can cause a range of adverse effects, such as growth inhibition, impaired reproductive capacity, endocrine disruption, and developmental abnormalities in freshwater fish, as evidenced by the present review. These investigations support the concept of Cd as a naturally available pollutant that causes irreversible damage in fish. These findings will help to understand the etiology of environmental circumstances that pose substantial dangers to fish health and are also crucial for preventing and treating exposure-related reproductive disturbances in freshwater fish due to environmental pollution.

To evaluate the impact of nutritional tea polyphenols (TPs) on body composition, growth, biochemical markers, antioxidant capacity, and hemato-immunological levels, a ten-week feeding experiment was carried out on coho salmon (Oncorhynchus kisutch, 180.51 ± 0.15 g). The control group was fed a basal diet; the T1, T2, T3, and T4 groups were fed 0.005%, 0.01%, 0.02%, and 0.04% TPs, respectively. These results demonstrate that adding TPs significantly (p < 0.05) increased the coho salmon fish’s weight gain (WG), relative growth rate (RGR), condition factor (CF), feed efficacy (FE), daily growth rate (DGR), and specific growth rate (SGR). There was no discernible difference in the body compositions of the treated TPs and the control group (p > 0.05). In addition, the T3 group showed a significant (p < 0.05) decrease in GPT, LDL, HDL, TC, and CAT. Fish given a 0.02% diet containing TPs had significantly lower levels of malondialdehyde (MDA) in their liver; yet, the TP-treated groups had higher levels of SOD and CAT than the control (p < 0.05). The data analysis shows a significant rise in lysozyme, respiratory burst activity, bactericidal activity, and blood hematological parameters in the 0.01–0.04% TP groups. According to these findings, TPs could be a useful dietary supplement for raising the antioxidant status, growth parameters, haemato-immunological response, and whole-body composition of coho salmon fish.

The increased prevalence of disease, mortality, and antibiotic resistance among aquatic microorganisms has renewed interest in non-conventional disease prevention and control approaches. Nanoparticles present several benefits in aquaculture and hold significant potential for controlling both human and animal infections. This study reports on the antibacterial properties of green copper oxide nanoparticles (CuO NPs) synthesized from the urine of Mithun (MU) (Bos frontalis). In addition, an array of analytical techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible spectroscopy (UV), and Fourier transform infrared spectroscopy (FTIR), were employed to investigate the synthesized MU-CuO nanoparticles. Aeromonas hydrophila and Aeromonas veronii, two bacterial fish pathogens known to cause severe infectious diseases in fish, were tested for their antibacterial efficacy against MU-CuO NPs. At 100 µg/mL, MU-CuO NPs exhibit enhanced antibacterial efficacy against two bacterial pathogens commonly found in fish. Applications in aquaculture may be looked at given that MU-CuO NPs showed greater antibacterial activity.