Journal of Fisheries

Antimicrobial resistance and phage sensitivity of Chryseobacterium sp. isolated from diseased rainbow trout (Oncorhynchus mykiss)

Mustafa Ustundag — 2025-12-23

This study aimed to isolate and characterize bacteriophages infecting Chryseobacterium sp., an opportunistic pathogen responsible for considerable mortality in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) aquaculture. Chryseobacterium isolates were recovered from diseased trout collected from aquaculture facilities in Mersin and Van (Türkiye) using Anacker–Ordal medium. Identification was performed through API 20E/20ZYM biochemical profiling and 16S rRNA gene sequencing. Antibiotic susceptibility was evaluated by the Kirby–Bauer disk diffusion method following CLSI and EUCAST guidelines. Phages were isolated from water samples via 0.22 μm filtration and purified using the double-layer agar method. Antimicrobial susceptibility testing revealed that Chryseobacterium isolates were sensitive to enrofloxacin, oxolinic acid, and ciprofloxacin, but exhibited pronounced resistance to most β-lactam and aminoglycoside antibiotics. A total of 19 lytic phages (CV1 – CV19) were successfully isolated. They displayed latent periods between 2.5 and 7.5 h and burst sizes ranging from 20 to 235 PFU per cell. The highest burst size and shortest latent period were recorded for the CV5 phage. Adsorption rate constants showed phage-specific variability, with overall values ranging from 1.05×10⁻⁶ to 2.55×10⁻⁶ mL·min⁻¹. Genome sizes were estimated at 48 – 75 kb. TEM revealed typical tailed morphologies consistent with the order Caudovirales. Host range assays showed strong species specificity, with limited cross-activity against Flavobacterium psychrophilum and Enterococcus faecalis. The findings confirm that these phages possess traits favorable for use as eco-friendly biocontrol agents, offering a promising strategy to mitigate Chryseobacterium-associated infections and reduce antibiotic dependence in trout hatcheries.

Assessment of fish consumption behaviour and market forecasts for sustainable fisheries in Manipur, India

N. K. Sonanla — 2025-12-18

This study analysed the socio-economic characteristics, consumption behaviour and expenditure patterns of fish-consuming households in Manipur, India, using data from 450 households across six districts belonging to different social background. Secondary data (2015 – 2025) obtained from government records supported a production-requirement forecast. The regression model demonstrated a moderately strong relationship between the predictors and the dependent variable (R² = 0.588; adjusted R² = 0.581). A paired t-test revealed that monthly expenditure on fish alone ₹5,326.88 (~59.20 $) was much higher than other non-vegetarian foods ₹2,310.44, comprising nearly 70% of the total non-vegetarian expenses. Holt’s exponential smoothing model (R² = 0.813, MAPE = 2.71%) projected that fish demand will exceed supply from 2024 – 2029, indicating a widening gap. The study concludes that fish holds cultural and nutritional importance in Manipur and calls for enhanced aquaculture, better market infrastructure, and improved consumer awareness for sustainable fish supply and food security.

Using brine shrimp to assess the performance of Annona muricata–zinc oxide nanoparticles: characterization and evaluation of photocatalytic, antibacterial and antibiofilm properties

Faiz Al Faiz — 2025-12-17

The development of multifunctional nanoparticles through green synthesis is an important advancement in nanotechnology, addressing the growing need for effective antimicrobial agents against drug-resistant pathogens and efficient photocatalysts for environmental remediation, while also necessitating thorough eco-toxicological assessments to ensure their safe application, particularly in sensitive ecosystems like fisheries. In this study, we investigated the antimicrobial activities, photocatalytic activity and eco-friendly assessment on zooplankton crustacean Artemia salina and phytochemical properties of biosynthesized zinc oxide nanoparticles using aqueous fruit extract of Annona muricata (Am-ZnO NPs). The synthesized Am-ZnO NPs was characterized using UV–visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). XRD analysis revealed the crystalline nature of Am-ZnO NPs. TEM analysis showed that the Am-ZnO NPs were spherical in shape with a size between 50 and 100 nm. In addition, Am-ZnO NPs showed antibacterial and antibiofilm activity against multiple drug resistance (MDR) Gram positive, Enterococcus faecalis bacteria. Am-ZnO NPs showed significant photocatalytic activity against two different organic dye pollutants namely methylene blue and acridine orange under both sunlight and UV light exposure. Ecotoxicity assessment of Am-ZnO NPs (25, 50, 75, and 100 μg mL^–1) showed no toxicity against non-targeted marine crustacean Artemia salina at low concentration and slightly toxic at high concentration (100 μg mL^–1). Together, the results suggest the potential application of Am-ZnO NPs against multiple drug resistance microbes and photocatalytic activities.

Investigation on the cypermethrin-induced genotoxic, biochemical, and antioxidant gene expression modulations in the gill tissue of Pethia conchonius, a resident fish of river Teesta, India

Debojit Dutta — 2025-12-15

Pesticides, an integral part of agricultural practices, contaminate aquatic bodies through surface runoff and leaching and threaten non-target organisms like fish. Synthetic pyrethroids, a widely used insecticide group have been shown to have detrimental effects on fish. Pethia conchonius, a non-target fish from river Teesta was used as a model organism to evaluate the detrimental effects of pyrethroid insecticide, cypermethrin on fish. The comet and micronucleus assays revealed cypermethrin-induced severe nuclear DNA damage showing three-fold decrease in % head DNA with a concomitant 70-fold increase in % tail DNA, and up to 21 times increase in MN frequency for SLC III at 96 hr exposure. The SOD, CAT, and GPx assays in gills and their mRNA expression analysis indicated down regulation of these anti-oxidant enzymes in a concentration and time-dependent response, with the lowest decrease being 4.2, 2.2, and 1.8-folds respectively for each of the enzymes at 96 hr of cypermethrin treatment in comparison to the control (p > 0.05). Subsequently, elevated levels of MDA in the gills of cypermethrin-treated P. conchonius further indicated increased oxidative stress and lipid peroxidation. Elevated oxidative stress and ROS levels can cause DNA damage and disrupt normal cell functioning, biochemical pathways, and cell cycle. The results indicated that cypermethrin is highly genotoxic and induces oxidative stress in the fish, supporting its hazardous effect on non-target organisms in aquatic ecosystems.

Growth and nutrient profile of Tetraselmis chuii under different urea concentrations: implications for sustainable uses

Md. Jahid Hossain — 2025-12-14

Nitrogen is regarded as one of the most important nutrients for algal cells, having a direct impact on the growth and biochemical contents of microalgae. The goal of this research was to compare the growth and proximate components of Tetraselmis chuii cultivated in various urea concentrations as an available source of nitrogen. Results disclosed that T. chuii cultivated in urea at 93.4 mg L^–1 N had higher cell density, biomass, and optical density compared to 11.67 mg L^–1, 23.35 mg L^–1, 46.7 mg L^–1, and 233.5 mg L^–1 N, respectively. Protein content was highly significant for urea at 233.5 mg L^–1 N concentration compared to other concentrations. In contrast, higher carbohydrate content was found at 11.67 mg L^–1 N compared to other concentrations of urea. Thus, the current study found that raising or decreasing urea concentrations had a substantial effect on the growth and proximate composition of indigenous marine T. chuii, and the highest biomass was recorded at 0.0145 g L^–1 (dry biomass) from 93.4 mg L^–1 N. These findings have implications for the cultivation of microalgae for various applications, including biofuel production, wastewater treatment, mariculture developments, and a sustainable blue economy in Bangladesh.