Journal of Fisheries

Alterations in Nile tilapia Oreochromis niloticus erythrometry as sensitive indicators of dietary fluoroquinolone antibiotic enrofloxacin toxicity

2026-06-19T08:16:53+00:00

The use of antibiotics in aquaculture poses significant health risks to fish and consumers. Adopting and validating a standard, non-lethal, and cost-effective method to monitor fish health is essential. This study investigated the impact of fluoroquinolone antibiotic enrofloxacin (ENF) on the erythrocyte cellular and nuclear morphometric anomalies in Oreochromis niloticus. Fish were fed graded doses of ENF at 0 mg, 10 mg, 30 mg, 50 mg and 100 mg kg biomass^–1 day^–1 for 15 consecutive days, followed by a 21-day post-dosing observation. The results revealed significant alterations in erythrocyte morphometric characteristics, such as major and minor axes, volume, surface area, cell to nucleus ratio, and surface area to volume ratio due to dietary ENF, indicating its cytotoxicity and perilous effects on fish erythrocytes. The nucleus was shrinking more significantly than the cell under treatment-induced stress. On day 15 of dosing, the surface area to volume ratio increased in the dosing groups, except for the 10× group, which represented an adaptive response in the fish to facilitate greater area for gas exchange to occur. However, the observed dose- and time-dependent erythro-morphometry was reversible once dosing was suspended. The results showed that fish erythrometric abnormalities, a relatively unexplored area of clinical science, can serve as important biomarkers or sensitive indicators of toxicity of veterinary medicinal products in assessing the physiological health status of cultured aquatic organisms.

Effects of photoperiod on growth and ovarian maturation in female green mud crab, Scylla serrata (Forsskål, 1775)

2026-06-18T08:16:46+00:00

Photoperiod is one of the most significant environmental cues for an organism, which are also essential for controlling its growth, metabolism, and maturity. The current study used an 8-week experiment to examine the effects of photoperiod T1 (12L∶12D), T2 (18L∶6D), and T3 (6L∶18D) on mud crab (Scylla serrata) growth performance and gonadal maturation. A total of 36 healthy crabs (average initial weight 416.18±2.42 g) were fed twice daily at 10% of body weight. Crabs cultured under 6L∶18D (T3) showed the highest final weight (486.54±4.44 g), weight gain (70.45±3.92 g), specific growth rate (0.26±0.01 % day^–¹), gonadosomatic index (12.06±0.20%), and hepatosomatic index (5.64±0.35%), significantly higher than T1 and T2. Digestive enzyme activities (amylase, protease, lipase) were highest in the 6L∶18D group, indicating efficient nutrient utilization. Ovarian carotenoid levels were significantly (p < 0.05) higher in 6L∶18D (0.4399±0.0640 µg mg^–1). Histology revealed advanced vitellogenesis and a healthy hepatopancreas in the 6L∶18D group, while the 18L∶6D showed delayed maturation. Overall, the results indicate that among the treatment groups, the 6L∶18D improved the growth, digestion, and reproductive performance of female S. serrata. This could be used in broodstock maturation, which has a detrimental effect on wild stock, and could offer valuable insights into sustainable broodstock management.

Biosafety improvement of aquaculture-associated bacteriophage preparations via endotoxin reduction: implications for Flavobacterium psychrophilum control

2026-06-18T08:16:57+00:00

The use of bacteriophages specific to Flavobacterium psychrophilum in aquaculture has shown promising results in controlling infections and reducing fish mortality. However, the biosafety and cytocompatibility of these phage preparations, especially under long-term exposure conditions, remain largely unexplored. In this study, bacteriophages specific to F. psychrophilum were isolated and characterized. To enhance biosafety, the phages were subjected to endotoxin reduction procedures. Endotoxin levels and phage titers were quantitatively determined before and after purification. Cytocompatibility was evaluated using the MTT assay on the mammalian cell line MCF-7 over a 120-hour exposure period. The purification process reduced endotoxin levels by 97.3%, while phage titers were preserved or increased, indicating that biological activity was maintained. Time-dependent analyses revealed that crude phage preparations caused a decrease in cell viability, with statistically significant reductions observed at 72, 96, and 120 hours (p < 0.05). In contrast, no difference in cell viability was observed in cells treated with purified phage preparations compared to the control group (p > 0.05). These findings demonstrate that the cytotoxic profile of phage preparations is determined by endotoxin content and prolonged exposure duration. This study highlights that endotoxin removal is critically important for ensuring cytocompatibility and demonstrates that endotoxin content in phage preparations used in aquaculture may lead to reduced cell viability in mammalian cells under long-term exposure conditions.

Modulatory effects of dietary vitamin E on bisphenol A toxicity in male Oreochromis niloticus: insights into oxidative stress, hepatic dysfunction, reproductive hormone and histological alterations

2026-06-17T08:17:02+00:00

The effectiveness of graded dietary vitamin E levels in alleviating bisphenol A (BPA) induced oxidative stress, hepatic dysfunction, reproductive hormone disruption and histological alterations in male Oreochromis niloticus was tested through a 45-day study using seven experimental groups: a negative control (C1; no BPA exposure; basal dose of 100 mg vitamin E kg^–1 diet), a positive control (C2; exposed to 0.04 ppm BPA; basal dose of 100 mg vitamin E kg^–1 diet), and five treatment groups: T1 (0.04 ppm BPA; 200 mg vitamin E kg^–1 diet), T2 (0.04 ppm BPA; 400 mg vitamin E kg^–1 diet), T3 (0.04 ppm BPA; 600 mg vitamin E kg^–1 diet), T4 (0.04 ppm BPA; 800 mg dietary vitamin E kg^–1 diet), and T5 (0.04 ppm BPA; 1000 mg vitamin E kg^–1 diet). Exposure to BPA resulted in haematological and antioxidant enzymes alterations with increased superoxide dismutase and catalase activities. Further, a decrease in 11-ketotestosterone and increase in estradiol levels was observed, which corresponded with pronounced histopathological damage in testicular tissue, including degeneration of seminiferous tubules and disrupted spermatogenesis. The dietary incorporation of 600 mg vitamin E kg^–1 diet produced most consistent improvement across physiological and endocrine parameters, along with near-normal testicular architecture in T3 group. Collectively, the findings demonstrate that dietary vitamin E effectively mitigates BPA-induced toxicity within an optimal range, emphasizing the importance of dose optimization for maintaining reproductive health in O. niloticus.

Effects of different carbon sources on the growth of freshwater zooplankton Moina micrura (Kurz, 1875) in biofloc system

2026-06-17T08:17:13+00:00

A 30-day study was conducted to evaluate the population growth of Moina micrura in biofloc systems using different carbon sources: jaggery, rice bran, tapioca, and coconut oil cake. Coconut oilcake and rice bran based biofloc system produced significant higher populations densities (15042±1018 and 13060±1010 individuals L^–1, respectively) compared to jaggery and tapioca. The optimal production was achieved at a C:N ratio of 20:1 and a floc volume of 5 mL L^–1, where peak population density was observed. M. micrura abundance showed a significant positive correlation (p ≤ 0.05) with water quality parameters pH, alkalinity, TAN-N, nitrite-N, and nitrate-N. Enhanced growth and reproductive performance in complex carbon based biofloc systems were attributed to improved nutrient availability and microbial composition. The findings demonstrate that nutrient rich biofloc systems, particularly those based on rice bran and coconut oil cake under optimized conditions, can be effectively utilized for mass culture of M. micrura, supporting improved live feed production in aquaculture.