The concentration of 23 metals was analyzed in the tissue of nine fish species, which represents the different habitats, i.e., primary feeder, tertiary feeder, and bottom feeder in fresh and marine waters of Visakhapatnam. Scomberomorus guttatus, Upeneus vittatus, and Penaeus indicus were selected in the coastal waters; Xiphias gladius, Stolephorus indicus, and Penaeus monodon from deep sea; and Channa striata, Puntius chola, and Macrobrachium rosenbergii from freshwater were analyzed. Metals in fish were analyzed by using the Inductive Couple Plasma Mass Spectrometer (ICP-MS). The concentrations of metals in fish were within the permissible limit set by WHO, FAO apart from Chromium, Aluminum, Manganese, and Arsenic. The concentrations were highest in coastal water fish and lowest in freshwater fish. Similarly, higher concentrations were observed in bottom feeders than in other tiers.

Consumption advice to ensure the health and safety of fish consumers remains urgent to handle the ever-increasing panic over heavy metal toxicity. Moreover, studies of fish consumption rarely focus on the perceptions and awareness of consumers. Considering this, the present study examines the factors determining the willingness to follow fish consumption advice as well as calculate the risk–benefit ratio and produce the vulnerability map followed by formulating fish consumption advice for consumers of two commercially important fish species, tilapia (Oreochromis niloticus) and mudfish (Ophiocephalus striatus), in the Laguna de Bay area of the Philippines. Primary data on consumers’ perceptions were collected through a questionnaire, whereas heavy metal contamination data were compiled from the best available literature. We concluded that people’s willingness to adopt consumption advice is mostly dependent on their existing level of fish consumption (P = 0.000). There was no discernible difference in the mean concentration of heavy metals in fish between the dry and wet seasons, with the exception of As concentrations in the samples (t15.75 = 3.72, p < 0.001). The hazard quotient (risk–benefit ratio) for fish consumption (HQefa) was an order of magnitude higher in the mudfish samples (0.05 and 28.28) compared to tilapia (0.04 to 16.02). Binangonan and Taguig from the Northern West Bay (1A, 1B) were clearly recognised on the vulnerability map as the most vulnerable regions in the lake. In general, it was determined that As and Pb were the elements causing consumption restrictions on tilapia collected from various parts of Laguna Lake. As with tilapia, locations with a high-risk advisory for mudfish were identified as the Northern West Bay and Central Bay, with a consumption limit of five meals per month due to excessive mercury pollution. This empirical study can serve as an option for the future development of fish consumption advice in the region.

The study was conducted to assess the histopathological impairment of gill and liver of freshwater snakehead murrel, Channa striata. The fish were exposed to sublethal concentrations (1.1 ppm) of insecticide Sevin for 30 days and a parallel control was run simultaneously. No histopathological effects were observed in control. Gill and liver of the exposed fish exhibited some remarkable alterations in their histology. Prominent changes include vacuolation, necrosis, epithelial lifting, shortening of lamellae, the fusion of adjacent lamellae, blood congestion, architectural distortion and degeneration of gills, lamellar fusion, hypertrophy, clubbing, few lamellar missing and shrinkage of blood vessels were observed in treated fishes. Hypertrophy of hepatocytes, necrosis, blood congestion, vacuolation, cellular degeneration, damage of nuclei was observed in the liver of exposed fishes. Duration of exposure of Sevin appears to have a reflective effect on gill and liver as with the increasing duration of exposure histopathological damages become more severe.

For the first time, we revealed the life-history traits including growth pattern (length–weight relationships, LWRs), condition factors, form factor (a₃.₀), first sexual maturity (Lₘ), age at first sexual maturity (tₘ), life span (tₘₐₓ), natural mortality (Mw), asymptotic length (L∞), and optimum catchable length (Lₒₚₜ) of ten commercially important small indigenous fish species (SIFS) in the Oxbow lake (Baor), southwestern regions of Bangladesh. A total of 1651 specimens were sampled during January to December 2020 with traditional fishing gears including seine nets, gill nets, and lift nets. Individual total length (TL) and body weight (BW) were measured by digital slide calipers and digital balance, respectively. To calculate the Lₘ, empirical maximum length-based model was considered, and Lₒₚₜ was calculated based on L∞. The TL vs. BW relationship indicated positive allometric growth for Chanda nama (Hamilton 1822), Channa punctata (Bloch 1793), Channa striata (Bloch 1793), Lepidocephalichthys guntea (Hamilton 1822), Macrognathus pancalus (Hamilton 1822), and Puntius sophore (Hamilton 1822), but negative allometric growth for Badis badis (Hamilton 1822), Gudusia chapra (Hamilton 1822), Glossogobius giuris (Hamilton 1822), and Hyporhamphus limbatus (Valenciennes, 1847). All r² values exceed 0.910 that indicated all LWRs were highly significant (P < 0.001). According to Spearman correlation test, Fulton’s condition factor (KF) vs. BW was highly correlated (P < 0.001), indicating better well-being for these species. Moreover, a₃.₀ indicates B. badis, C. punctata, C. striata, G. giuris, H. limbatus, L. guntea were elongated; C. nama, P. sophore, were short and deep; G. chapra was fusiform, and M. pancalus was eel-like body shape respectively. The minimum tₘ and tₘₐₓ were obtained as 0.74 year and 2.66 year for C. striata and maximum were 0.93 year and 3.31 year for B. badis, respectively. This study provided information on tₘ and tₘₐₓ for ten SIFS that is globally absent. From empirical models, the smallest mean value of Lₘ was found for B. badis (3.98 cm), and the greatest was found for C. striata (16.96 cm). The minimum Lₒₚₜ was obtained as 3.78 cm TL for B. badis and maximum was 14.09 cm TL for C. punctata. The minimum Mw was documented as 1.39 for B. badis and maximum was 1.73 for C. striata. The output of this research will be helpful for developing sustainable management policies and protection of SIFS through the application of mesh size based on Lₘ and Lₒₚₜ in the Oxbow lakes, Bangladesh and neighboring countries.

Nanotechnology is a novel arena with promising applications in the field of medicine, industry, and agriculture including fisheries. Cross-disciplinary interactions and the application of this technology in biological systems have led to the innovation of novel nanoparticle antioxidants, which are the subject of our study. In context with above background, we designed an experiment on nano-silver to elucidate its role for mitigation of abiotic and biotic stress. Three diets were formulated viz. silver nanoparticles (Ag-NPs) incorporated at 0.5 and 1 mg/kg diet and control diet (Ag-NPs at 0 mg/kg). Fish were exposed to sublethal level of 1/25th of LC₅₀ (4 ppm) of lead (Pb) and temperature at 34 °C. The effect of Ag-NPs on productive performance (weight gain %, feed conversion ratio, protein efficiency ratio, and specific growth rate), stress biomarkers (catalase, super oxide dismutase, glutathione-s-transferase, acetylcholine esterase, cortisol, heat shock protein), biochemical and immunological response (protein and carbohydrate metabolic enzymes, phagocytic activity, serum total protein and albumin: globulin ratio), histopathology alterations in the liver and gill as well as survival of Channa striatus, following challenge with pathogenic bacteria were evaluated. Dietary Ag-NPs at 0.5-mg supplementation improved growth performance, immunity, survival, and reduced stress biomarker such as HSP 70, cortisol, and blood glucose in various fish tissues. Exposure to Pb and high temperature and group fed with Ag-NPs (1 mg/kg diet) demonstrated remarkable changes in the histo-architect of liver such as pyknotic nuclei, pyknosis, leucocyte infiltration, hemorrhage and karyokinesis, blood vessels with nucleated, lipid vacuoles in the liver tissue. Histology of gill displayed hyperplasia, aneurism, blood congestion, severe telengiectiasis, epithelial lifting, curling of secondary lamella, hyperplasia of epithelial cell of secondary lamella in the group exposed to lead and high temperature and supplemented with Ag-NPs at 1 mg/kg diet. In addition to histopathology, feeding with Ag-NPs at 1 mg/kg diet deteriorated and altered all studied parameters including reduced growth performance. Results obtained in the present study suggest that supplementation of Ag-NPs at 0.5 mg/kg diet has a definitive role to play in the mitigation of abiotic and biotic stress in C. striatus.

The cytotoxicity, genotoxicity and oxidative stress of malachite green (MG) was investigated using the fish Channa striata kidney (CSK) and Channa striata gill (CSG) cell lines. Five concentrations ranging from 0.001 to 10 μg mL⁻¹were tested in three independent experiments. Cytotoxicity was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Rhodamine 123 and Alamar Blue. The mitochondrial changes and apoptosis of MG-exposed cells were observed by Rhodamine 123 and acridine orange/ethidium bromide (AO/EB) staining, respectively. In vitro potential DNA damaging effect of MG was tested using comet assay. Mitochondrial damage, apoptosis and DNA fragmentation increased in a concentration-dependent manner. Additionally, DNA electrophoretic mobility experiments were carried out to study the binding effect of MG to double-stranded DNA (dsDNA) of cells. DNA shift mobility experiments showed that MG is capable of strongly binding to linear dsDNA causing its degradation. Biochemical parameters such as lipid peroxidation (MDA), catalase (CAT) activity and reduced glutathione (GSH) levels were evaluated after exposure to MG. In CSK and CSG cell lines exposed to MG for 48 h, a significant increase in lipid peroxidation, which might be associated with decreased levels of reduced glutathione and catalase activity in these cell lines (p < 0.001), was observed.