The occurrence and impact of pathogenic Vibrio sp. in coastal waters are strongly influenced by climate change indicators such as ocean warming, sea-level rise, and extreme weather events. This study aimed to compare the virulence and antimicrobial resistance (AMR) profiles of Vibrio cholerae from clinical and environmental sources across India's coastal regions. We also examined pathogenic traits in other marine Vibrio sp. We hypothesized that Vibrio spp. from different environments would show distinct virulence and AMR patterns shaped by their ecological context. To investigate this, we conducted antimicrobial susceptibility testing and whole-genome sequencing (WGS) on both clinical and environmental isolates. Our findings reveal that environmental V. cholerae from coastal waters possess genes promoting host adhesion and haemolytic activity. Similarly, Vibrio alginolyticus and Vibrio vulnificus harboured virulence factors aiding tissue attachment and invasion. Resistance profiling showed environmental V. cholerae were resistant to fluoroquinolones and macrolides, while clinical isolates were resistant to aminoglycosides and sulphonamides. The presence of antibiotic-resistant Vibrio in marine environments poses a significant public health risk, especially given frequent human interactions with coastal waters for recreation, fishing, and transport. Climate change may exacerbate the proliferation and movement of these pathogens across aquatic and terrestrial systems, increasing the likelihood of human exposure. Moreover, the potential for horizontal gene transfer of resistance genes among pathogenic marine bacteria further highlights the need for surveillance and mitigation strategies to address the growing threat of AMR in marine ecosystems.

Read More...

The present study was envisaged to generate prime information on the life history, biological characteristics, and stock status of the critically endangered smoothback guitarfish (Rhinobatos lionotus) that forms a fishery along the northwestern Bay of Bengal using length-based methods. The stock was predominantly represented by the females (Male: Female = 1:1.71). The species exhibited sexual dimorphism, where females grew bigger (Lmax = 79.0 cm) and matured at a larger size (LM50 = 43.71 cm) than males (Lmax = 61.0 cm, LM50 = 34.93 cm). Growth was allometric, where females were heavier compared to males. The life history characteristics, i.e., L∞, K, t0, M, and LC50 were 84.31 cm, 0.43 y−1, − 0.45 yr, 0.88 y−1, and 35.31 cm, respectively. The LBB analysis showed that the current biomass (B/B0 = 0.39) exceeded the level needed for maximum sustainable yield (BMSY/B0 = 0.35). The Lmean and LC50 were lower than the Lopt and LCopt, indicating growth overfishing. A sensitivity analysis revealed that the outputs of the Thompson and Bell model are highly influenced by uncertainties associated with L∞, followed by LC50, M, and K. The Thompson and Bell model revealed that the Fcurrent has depleted the SSB to a 35% level and therefore should be reduced by 18–19% to circumvent growth-overfishing (F0.1) and recruitment-overfishing (F0.4), respectively. Considering the multi-species nature of the fisheries in the region, focusing on spatial and temporal closures and strict implementation of by-catch reduction devices in the trawls are advised for the conservation and sustainable management of the species.

Read More...

Morphological changes during metamorphosis from larvae to juvenile stage vary considerably among teleosts. Metamorphosis in Acanthopagrus berda, a commercially important sparid, recorded using simple microscopy in captivity, revealed progressive changes in pigmentation, band formation, development of fins, and other morphological features. Larvae on 2 day post hatch [dph] (2—3 mm total length [TL]) exhibited an open mouth and pigmented eyes, and on 12 dph (6—7 mm TL), notochord flexion initiated with marked development in dorsal, anal and caudal fin formation. Larvae on 8 dph (3—4 mm TL) exhibited an initial internal pigmentation in the buccal cavity and 10 dph larvae were observed with an initial external pigmentation on the cephalic region. On 22 dph (11—12 mm TL), vertical band formation was initiated at the anterior portion of the larval body and proceeded posteriorly. The sequence of fin formation was in the order of pectoral, caudal, dorsal and anal fins, followed by the pelvic fin. On 45 dph (25—28 mm TL) miniature adult with fully formed silvery scales and lateral line emerged in captivity. TL bared a positive correlation with the larvae's vertical mouth opening and eye diameter. The coefficient of variation in body weight of the fish has reduced from 38 to 25% from larvae to juvenile. Information on the metamorphosis of the larvae of the species will help to act as an identification key for planktonic larvae collected from the natural environment.

Read More...

The present study documented a bloom of the comb jelly Beroe ovata occurring off Devaneri Kuppam in Mahabalipuram, close to Chennai. The abundance of the B. ovata bloom was estimated as 342 ± 21 individuals per cubic metre. A negligible number of hydromedusae specimens mixed with the comb jelly were also observed. The abundance of its predatory fish, the black pomfret (Parastromateus niger), the hydrozoan jellyfish (Aequorea pensilis), and the scyphozoan jellyfish (Cyanea nozakii) would be positively correlated with the sudden disappearance of the bloom of B. ovata on 10 October 2024. Following the bloom of B. ovata, the abundance of A. pensilis and C. nozakii led to a depletion of copepods, the main predators of dinoflagellates and diatoms, favouring the bloom of Noctiluca scintillans.

Read more...

India’s deep-sea fisheries are expanding rapidly, yet understanding of species diversity, resource availability, and conservation needs remains limited. This study examines the diversity and seasonal-temporal variation of deep-sea finfishes in the Quilon Terrace region (200–500 m depth) based on bycatch data from deep-sea shrimp trawlers collected between 2020 and 2022. A total of 144 finfish species were identified, spanning 3 classes, 31 orders, 76 families, and 108 genera. The most abundant orders were Perciformes (17.52%), Acropomatiformes (16.93%), and Scombriformes (15.58%). Biogeographically, 2 species had circumtropical and 8 circumglobal distributions, while 18 were restricted to the Indian Ocean and 22 to the Western Indian Ocean. The blackmouth splitfin (Synagrops japonicus) dominated catches in all three years (up to 19.47%), while myctophid Diaphus watasei became dominant in 2022 (26.99%). A notable presence of apex predators occupying trophic levels 4.0–4.5 was recorded. Marked seasonal differences were observed in diversity and species composition between pre- and post-monsoon periods, with limited interannual variation. Trophic structure and variability were also analyzed. Conservation analysis showed 21.5% of species were IUCN Data Deficient, and 4.6% fell under threatened categories, including Near Threatened, Vulnerable, Endangered, and Critically Endangered. The observed rise in mesopelagic species diversity in landings suggests increasing commercial interest in these resources, emphasizing the need for sustainable management and targeted conservation strategies.

Read more...