Journal of Fisheries

Spatial variation in the otolith shape of Asian sheat catfish, Wallago attu (Bloch & Schneider, 1801) populations from five Indian rivers

Graish Kumar, Ankur Kashyap, Mohammad Serajuddin — Mon, 09 Mar 2026 11:55:42 +0000

The population of Wallago attu (Bloch & Schneider, 1801) has declined worldwide including in the rivers of India and has been declared ‘Vulnerable’ by the International Union for Conservation of Nature. The restoration and conservation of fishes is heavily dependent on their population status in their natural habitats. Therefore, otolith shape was used to study the stock structure of W. attu from rivers Ganga, Gomti and Yamuna in Northern India, river Hooghly in Eastern and Pampa in Southern part of India. Shape indices of the asteriscus otoliths and elliptical Fourier analysis of the contour shapes was investigated using univariate and multivariate statistical techniques. The otolith descriptors (otolith length, breadth, area and perimeter) and four shape indices (length-breath ratio, form factor, circularity and ellipticity) of the otoliths were different (ANOVA, p<0.05) between the fish of five sampled rivers. Principal component analysis of normalized elliptical Fourier descriptors (NEFDs) of the contour shape accounted for 89.55% of the total variance. Discriminant function analysis on the basis of NEFDs resulted in 100% classification rate with no intermixing between the fish of different rivers and depicted the presence of different stocks of W. attu in a scatter plot of DF-I against DF-II. These variations in the otolith shape in the current study might be due to the restricted movement of fish because of geographical isolation and different environmental conditions in different rivers due to changes in habitat, or both. The current study would be helpful in developing effective strategies for stock management of this species.

Pathogenicity and molecular characterization of cyprinid herpesvirus-2 (CyHV-2) infecting Hypophthalmichthys molitrix in India

Supratim Malla, Himadri Saha, Lija Ghosh — Mon, 09 Mar 2026 11:28:34 +0000

Cyprinid herpesvirus-2 (CyHV-2), a linear double-stranded DNA virus of the genus Cyprinivirus (family Alloherpesviridae), is a significant pathogenic agent responsible for herpesviral hematopoietic necrosis disease (HVHND), causing severe mortality in cyprinid fishes. While CyHV-2 is well documented in goldfish and crucian carp, information on its pathogenicity in Chinese carps remains limited. The present study investigated a severe disease outbreak in carp polyculture systems, with a focus on Hypophthalmichthys molitrix, integrating epidemiological observations, pathology, molecular characterization, and experimental infection trials. Affected fish exhibited clinical signs, including lethargy, hemorrhages, and respiratory distress, accompanied by extensive gross and histopathological lesions involving the gills, kidney, spleen, and musculature. CyHV-2 was detected by PCR in both diseased and apparently healthy fish, suggesting subclinical infection or transient viral presence. Sequence analysis of the partial DNA polymerase gene showed 94.95% identity with the virulent Asian strain CNDF-TB2015 and clustered within the CyHV-2 clade, confirming the virus identity. Experimental infection using tissue-derived inocula showed differential pathogenicity, with kidney (upto 80%) and gill-derived inocula (70%) inducing significantly higher mortality (log-rank test, p < 0.005) than liver-derived inocula (10%). Bacteriological analysis revealed concomitant Aeromonas infection, suggesting viral-bacterial synergism during disease outbreaks. Collectively, the findings implicate CyHV-2 as a primary viral agent involved in the outbreak and highlight kidney and gill tissues as critical targets for pathogenesis. This study provides the first integrated pathological, molecular, and experimental evidence of CyHV-2 pathogenicity in carp polyculture systems and underscores the need for routine surveillance to mitigate emerging viral threats in aquaculture.

Microplastic pollution in edible marine fish from the northwestern Bay of Bengal, Bangladesh: A comprehensive assessment of occurrence, characteristics and associated ecological risks

Wed, 04 Mar 2026 17:55:39 +0000

Microplastic (MP) pollution is an emerging environmental issue with serious implications for marine ecosystems and potential risks to human health. This study assessed MP contamination in the gastrointestinal tracts of 130 individuals representing 13 species (n=10 species^–1) from the Bay of Bengal, Bangladesh. A total of 892 MP particles were detected, confirming ubiquitous contamination across all species. MP abundance ranged from 3.70–12.00 items per individual (mean±SD: 6.87±1.08 items fish^–1). Five morphotypes: fibers, films, foams, pellets, and fragments were identified, with fibers constituting the dominant category. Most MPs were <5 mm, and red was the most common color. MP abundance exhibited a moderate positive correlation with body length (r=0.41), indicating that larger individuals tended to contain higher numbers of MP. Benthopelagic species exhibited the highest MP ingestion (7.85±2.58 items fish^–1), while carnivorous fishes showed greater contamination (7.13±2.59 items fish^–1) among trophic guilds. Risk assessment revealed that contamination factor (CF) ranged from 1.00–3.24, indicating moderate to high levels of MP contamination. The overall polymer load index (PLI) was 1.76, corresponding to a low pollution risk category. However, polymer hazard index (PHI) analysis revealed dominance of moderate-risk polymers, including polyester and PP–PE copolymer, with high-risk polymers such as nylon (PHI = 8.80) and PVC (PHI = 7.00) contributing substantially to overall hazard. These findings provide baseline evidence of MP contamination in Bangladeshi marine fisheries and highlight the need for future studies integrating polymer toxicity, trophic transfer, and human exposure pathways to support effective mitigation strategies.

Sustainable freshwater fisheries in Bangladesh: problems and pathways forward

Sanzida R. Swarna, Md. Yeakub Ali, Shams M. Galib — Mon, 02 Mar 2026 22:24:06 +0000

Bangladesh is one of the leading countries in global fish production; however, numerous problems and challenges persist. This paper summarises the problems faced by seven major stakeholder groups in the country’s fisheries sector: (i) fish farmers, (ii) freshwater fishermen, (iii) fish traders, (iv) fish seed producers, (v) fisheries administrators and extension personnel, (vi) researchers and (vii) fish consumers. Fish farmers reported 19 problems, with transportation issues being the most common (35% of respondents), followed by the lack of quality fish seed (20%). Freshwater fishermen reported 13 problems, with reduced fish catch as the most common (65%), followed by the shrinkage of fishing habitats (15%). For freshwater fish traders, lack of preservation and storage facilities was the most common problem, reported by 80% of respondents. Seven problems were reported by finfish seed producers; among the top-ranked, lack of quality brood and its high price were most common, reported by 60% and 40% of respondents respectively. Fisheries administrators and extension personnel reported nine problems, with insufficient manpower being the most common, reported by 70%. Eleven problems were reported by fisheries researchers, with inadequate research funding as the most common, reported by 60%. Fish consumers reported five problems, including price hikes and insufficient supply of native fishes. The results of this study will be useful in prioritising problems and formulating effective policies for the sustainable development of the fisheries sector in Bangladesh and other countries facing similar challenges.

Farm to policy: Socioeconomic dynamics and occupational challenges of freshwater fish farmers in the Cauvery Delta region, Tamil Nadu

S. Dawood Ibrahim, V. Senthilkumar, T. Umamaheswari, R. Durairaja — Fri, 20 Feb 2026 00:00:00 +0000

Freshwater aquaculture is vital for global food security and rural livelihoods. This study examined 120 fish farmers across Thanjavur, Thiruvarur, and Nagapattinam districts in Tamil Nadu's Cauvery Delta to understand socioeconomic dynamics and constraint hierarchies shaping aquaculture development. Using structured interviews and Garrett ranking, the research revealed critical structural vulnerabilities: the farming population is predominantly male (93.3%), aging (average 45 years; 79.2% middle-aged or older), and faces future labour succession challenges despite relatively high literacy (85% educated). Low organizational participation (54.2% non-members) undermines collective bargaining capacity. Most farmers (80.8%) combine aquaculture with other occupations, reflecting income insufficiency rather than strategic diversification. With 65% representing first-generation farmers averaging eleven years' experience, aquaculture emerges as recent livelihood diversification rather than traditional practice. Landholding patterns showed 75% farm ownership averaging 3.5 acres, though 53.3% operate small farms below three acres, limiting economies of scale. Caste composition revealed predominance of marginalized communities—61.7% Other Backward Class and 27.5% Scheduled Caste—facing systematic barriers to credit, technology, and market access. Constraint analysis identified high feed costs as the primary short-term barrier across all districts, followed by insufficient credit access and inadequate extension services, while low farm gate prices emerged as the dominant long-term constraint. Findings demonstrate that effective aquaculture policies must address structural inequities rooted in caste-based exclusion, land fragmentation, organizational deficits, and market asymmetries through targeted interventions including collateral-free credit, farmer producer organizations, district-level feed cooperatives, and differentiated extension programming to transform aquaculture into dignified, profitable livelihoods.