The deep-sea caridean shrimp Plesionika semilaevis (Spence Bate, 1888) is a significant commercial species in the deep-sea fishery on the south-west coast of India. Analysis of its population parameters is crucial for understanding variability and ensuring the sustainability of this stock. This study presents the first stock assessment of P. semilaevis from Indian waters, analysing its population and growth parameters in the south-eastern Arabian Sea. Both sexes showed negative allometric growth. Growth estimates using the von Bertalanffy model revealed fast growth and low longevity for males (L∞ = 14 cm TL, K = 0.74 yr-1 and Φ′ = 2.16) and females (L∞ = 14.3 cm TL, K = 0.73 yr-1 and Φ′ = 2.17). The length at first capture was estimated as 9.46 cm while the length at maturity was measured at 8.73 cm. The estimated values for natural, fishing and total mortality were 1.12 , 2.06 and 3.18±0.17 yr-1 respectively. The exploitation rate (E = 0.65) was almost equal to the Emsy value (E0.1 = 0.62), indicating the fishery as sustainable. The findings provide a baseline for stock management and conservation of Indian deep-sea fisheries.

Readmore.....

The dynamics of physico-chemical, nutrient, and chlorophyll-a variables were studied in the bloom and non-bloom locations along the off-Gujarat coastal waters to understand the variability in biogeochemistry using multivariate analytical tests. The dissolved oxygen was significantly lower in the bloom stations (3.89 ± 0.44 mgL−1) than in the non-bloom stations (5.50 ± 0.70 mg L−1), due to the biological degradation of organic matter in addition to anaerobic microbial respiration. Nutrients (PO4 and NO3) and Chl-a concentrations were recorded higher in the bloom locations at 0.83 ± 0.21 µmol L−1, 4.47 ± 0.69 µmol L−1, 4.14 ± 1.49 mg m−3, respectively. PO4 and NO3 have shown a significantly higher positive correlation of r = 0.73 and r = 0.69 with Chl-a for bloom data than the non-bloom data. The percentage variance contributed by PC1 and PC2 for both bloom and non-bloom locations were estimated at 52.33%. The variable PO4 explains the highest 24.19% variability in PC1, followed by Chl-a (19.89%). The PO4 triggers the bloom formation and also correlates to the higher concentrations of Chl-a in the bloom locations. The bloom concentration ranges from 9553 to 12,235 trichomes L−1. The bloom intensity has shown a significant positive correlation with Chl-a (r = 0.77), NO3 (r = 0.56), and PO4 (r = 0.30), but a negative correlation was noticed with DO (r =  − 0.63) and pH (r =  − 0.49). The study also initiates a way forward research investigation on ocean-color technologies to identify and monitor blooms and climate change–driven factors for bloom formation. The occurrence of bloom and its influence on fishery resources and other marine biotas will open many research windows in marine fisheries, oceanography, remote sensing, marine biology, and trophodynamics.

Readmore....

This pioneering study examined the wound healing and regeneration abilities of the upside-down jellyfish Cassiopea at the Cnidarian Laboratory of the ICAR-Tuticorin Regional Station, Central Marine Fisheries Research Institute (CMFRI), India. A total of nine specimens (5.8 ± 0.4 cm) were studied, including six control medusae, one accidentally injured jellyfish (cut into four unequal fragments), and two amputated jellyfish (each divided into four equal fragments, totalling eight fragments). All specimens were maintained in a recirculatory aquarium system under optimal seawater conditions. Species identification of the control was confirmed through Basic Local Alingment Search Tool (BLAST) analysis of the 16S rRNA gene, showing 98.91% similarity with Cassiopea xamachana (Bigelow 1892), from the United States of America (USA) GenBank Accession No. ON545804.1, and validated through phylogenetic analysis. Microscopic and morphological observations revealed that the oral arm tissue lacked pulsing activity and could not regenerate its body structure. In contrast, fragments of umbrella tissue from both amputated and injured specimens exhibited pulsing and successfully regained symmetry within 7–15 days. The first phase of self-healing involved the reformation of umbrella symmetry, regeneration of bell tissue, and resumed functions similar to those of the normal medusa. The development of canal systems, including anastomosing vessels radiating from the centre, oral arms extending from the mouth, vesicles from the arms, and the central disc, was documented. The experimental observations revealed sequential wound healing through regeneration and morphogenesis in amputated and injured medusa. This study established Cassiopea as a promising cnidarian model organism for regeneration studies, highlighting its remarkable self-repairing and regenerative capabilities.

Readmore........

Deep-sea trawl samples collected from the west coast of India have revealed several previously undetected species inhabiting the deep waters. This study reports the first record of Bathycongrus nasicus from the western Indian waters and the second record from the entire western Indian Ocean. A single specimen of B. nasicus was collected from the Neendakara fishery harbour in southern Kerala. The species identity was confirmed morphometrically by comparing it with previous records, and the study provides the first molecular identification of this rare congrid eel. The presence of B. nasicus in the western Indian waters suggests its potential distribution throughout the northern Indian Ocean, with prior records from the Bay of Bengal and the western Arabian Sea. This new record indicates that there might be occurrences of several previously unknown fish species in the non-commercial fishery of this region, underscoring the importance of survey collections of non-commercial fishes, which play a crucial role in marine ecosystems.

Readmore.....

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...