Journal of Fisheries

Deciphering the phyto-immunomodulatory potential of orange (Citrus sinensis) peel in goldfish (Carassius auratus) diet against Aeromonas hydrophila

2026-07-27T08:30:53+00:00

The increasing demand for sustainable and functional feed additives in aquaculture has driven interest in agro-industrial by-products such as orange (Citrus sinensis) peel, which are rich in bioactive compounds. This study investigated the effects of dietary orange peel supplementation on growth performance, digestibility, physiological responses, and disease resistance in goldfish Carassius auratus. Fish were fed diets containing 0% (control), 2.5%, 5%, and 7.5% orange peel for 60 days, followed by analyses of growth, digestive enzymes, haematological, biochemical, immunological parameters, and a pathogen challenge test. Results showed that the 2.5% inclusion level significantly enhanced growth, with approximately two-fold higher weight gain and improved feed conversion ratio (ANOVA: p < 0.05). Protein digestibility increased by ~20% in 2.5% and 5% groups, while digestive enzyme activities, particularly amylase (~120% increase) and protease (~25% increase), were markedly elevated. Haematological indices (RBC, HB, HT) improved significantly (p < 0.001), while glucose, triglycerides, and cholesterol were reduced in higher inclusion groups (p < 0.001). Antioxidant (SOD, CAT) and immune responses (NBT, MPO) were significantly enhanced (p < 0.001), indicating improved oxidative stress resistance and immune competence. Carotenoid deposition increased significantly in muscle (~24%) and skin (~23%). Following Aeromonas hydrophila challenge, survival improved up to 1.7-fold in supplemented groups (p < 0.05). Overall, the results demonstrate that orange peel, particularly at 2.5% inclusion, serves as an effective, sustainable functional feed additive that enhances growth, physiological health, and disease resistance, offering practical implications for improving aquaculture productivity and resilience.

Pathogenicity and systemic virulence of Aeromonas veronii in red-bellied pacu (Piaractus brachypomus): an experimental disease model

2026-07-25T08:30:16+00:00

Aeromonas veronii is an important etiological agent of motile aeromonas septicemia (MAS) in aquaculture; however, its pathogenicity in the emerging cultured species red-bellied pacu (Piaractus brachypomus) remains poorly understood. Pacu fingerlings (10±2 g; n = 180) were intraperitoneally challenged with A. veronii strain BLB-01 (GenBank accession: MF370515) at concentrations ranging from 10⁵ to 10⁹ CFU mL⁻¹, following OECD guideline 203. The median lethal dose (LD₅₀) was estimated using probit analysis. Clinical signs, haematological and biochemical parameters, and histopathological alterations were evaluated at 96 h post-LD₅₀ exposure. Probit analysis (Y = 0.591 + 2.185 log₁₀ concentration; R² = 0.984) estimated the LD₅₀ as 7.8×10⁶ CFU mL⁻¹ (95% CI: 5.2–11.4 ×10⁶ CFU mL⁻¹). Infected fish exhibited progressive MAS symptoms over 7 days. Haematological analysis revealed significant anaemia (decreased haemoglobin and total erythrocyte count), leukocytosis (increased total leukocyte count), and thrombocytopenia (reduced platelet count). Biochemical changes included stress-induced hyperglycaemia (elevated glucose), hepatocellular damage (increased ALP, AST, and ALT), and hypoalbuminemia (reduced albumin). Histopathological examination demonstrated severe lesions, including gill lamellar fusion (2.8±0.3), hepatic vacuolation (2.9±0.2), and renal tubular necrosis (2.8±0.2). Aeromonas veronii exhibits high pathogenicity in pacu, with an LD₅₀ of 7.8×10⁶ CFU mL⁻¹, providing baseline data for challenge studies and the development of vaccines and probiotics. A combination of haematological and biochemical markers particularly increased TLC, reduced platelet count, and elevated liver enzymes offers a practical tool for rapid field-level diagnosis and surveillance of MAS, supporting improved health management in Indian pacu aquaculture.

The blue economy paradigm: livelihood viability of fisherfolk through coastal tourism

2026-07-25T08:30:27+00:00

Coastal tourism is increasingly recognized as a vital component of the global 'blue economy', offering a critical pathway for traditional fishing communities to diversify their livelihoods amid mounting economic and environmental pressures. To understand this dynamic, this study investigates the occupational transition of 120 coastal fisherfolk into the tourism sector across two states in India. Analyzing socio-economic profiles and transition patterns, the research highlights a significant occupational shift, with 85.8% of respondents now identifying tourism as their primary income source. Demographically, the participants are predominantly middle-aged males with low educational attainment and modest living conditions. Fisherfolk strongly favor tourism over traditional fishing, citing lower physical strain, reduced risk, and more stable earnings. Consequently, this transition has led to a marked reduction in fishing labor hours and a significant income boost, with median annual tourism earnings reaching ₹252,000 (~USD 2610). Furthermore, data models reveal that a willingness to step away from traditional fishing is the strongest predictor of transition readiness. Despite these positive economic outcomes, the occupational shift is hindered by several major constraints. Disruptions from the COVID-19 pandemic, high initial investments, strong competition from established operators, poor infrastructure, and adverse weather conditions remain significant challenges. Ultimately, while tourism is increasingly central to diversifying coastal livelihoods and reducing heavy physical labor, ensuring its sustainability requires targeted interventions. Stronger institutional support, comprehensive skill development, and accessible financial mechanisms are essential to secure equitable, long-term benefits for these coastal communities.

Effect of L-proline supplementation on long-term cryopreservation of Piaractus brachypomus sperm: post-thaw motility, viability, and morphological assessment of sperm

2026-07-25T08:30:38+00:00

Sperm cryopreservation is widely used in aquaculture for long-term preservation of genetic resources and broodstock management; however, prolonged storage can adversely affect sperm quality due to structural damage and ionic imbalance. This study evaluated the influence of L-proline supplementation, with and without dimethylsulfoxide (DMSO), on the cryopreservation efficiency of Piaractus brachypomus sperm. Milt from hormonally induced males was cryopreserved in Modified Cortland Medium (MCM) supplemented with 2, 5, 10, and 30 mM L-proline, either in the absence of DMSO or in combination with 10% DMSO, and maintained under liquid nitrogen for 90 days. Sperm quality after thawing was evaluated at 15-day intervals. Significant differences were observed in sperm motility and viability among treatments. Among the MCM supplemented with L-proline treatments, 10 mM L-proline maintained the highest post-thaw sperm motility (58.05–53.40%) and viability (62.50%), whereas the MCM without cryoprotectant showed the lowest values. Among the MCM containing 10% DMSO treatments, 10% DMSO and 10% DMSO + 2 mM L-proline maintained comparatively higher post-thaw sperm motility (54.36–51.04% and 56.44–49.75%, respectively), whereas other groups exhibited higher post-thaw sperm viability (>52%) than the other DMSO-based treatments. Although a progressive decline in sperm quality was observed over the 90-day storage period, L-proline-supplemented groups maintained superior functional performance. Morphological assessment showed better preservation of sperm head integrity and fewer structural abnormalities in the 10 mM L-proline treatment compared to other cryopreserved treatments. The findings indicate that supplementation with 10 mM L-proline enhances sperm membrane stability and overall cellular function during cryostorage.

Effect of dietary L-ascorbic acid and L-leucine and their combination on growth performance, survival and feed utilisation in Labeo catla fingerlings

2026-07-25T08:30:49+00:00

The present investigation was carried out for a period of 75 days to evaluate the effects of dietary supplementation of L-ascorbic acid and L-leucine on growth performance and feed utilisation in Labeo catla fingerlings. A total of nine experimental diets were formulated with different levels of L-leucine and L-ascorbic acid, including a control (T₀) without supplementation. The treatments consisted of T₁ (10 g L-leucine), T₂ (15 g L-leucine), T₃ (0.3 g L-ascorbic acid), T₄ (0.4 g L-ascorbic acid), T₅ (0.3 g L-ascorbic acid + 10 g L-leucine), T₆ (0.4 g L-ascorbic acid + 10 g L-leucine), T₇ (0.3 g L-ascorbic acid + 15 g L-leucine) and T₈ (0.4 g L ascorbic acid + 15 g L-leucine). The results indicated significant improvement in the highest final weight (3.86±0.38 g), specific growth rate (1.95±0.10% day^–1), and protein efficiency ratio (1.74±0.08), along with the lowest feed conversion ratio (1.93±0.09) in T₆. The combination of 0.4 g L-ascorbic acid and 10 g L-leucine (T₆) was found to be the most effective and is recommended for enhancing growth and feed utilisation in L. catla fingerlings.