This study investigates the relationship between the seasonal availability and seasonal body length variation of Euthynnus lineatus (Black skipjack) with respect to the sea surface temperature (SST) variability and chlorophyll-a (Chl-a) concentration along the southern Pacific coast of Mexico, from October 2022 to October 2024. The region experiences two distinct seasons: a dry season with strong “Tehuano” winds causing upwelling, and a rainy season influenced by the Costa Rica Coastal Current. High-resolution satellite data were integrated with biometric and catch data from local artisanal fisheries. Seasonal catch patterns peaked between April and July, following increased productivity and rising SST. The highest catches coincided with SST around 31.0 °C, suggesting a thermal association that enhances aggregation and catchability. Significant interannual variability was observed; 2023 catches were more than double those of 2024, likely associated with the presence of a warm pool in 2023 and varying environmental conditions. Morphometric analysis indicated larger individuals in the catches during cooler, productive months (October-March) and smaller fish during warmer periods, possibly due to temperature-driven metabolic responses influencing their presence in coastal waters. Principal component analysis (PC1: 38.4
This study presents the first molecular identification of Pyrophacus horologium outside the Pacific Ocean, supported by a comprehensive morpho-molecular characterization. It was conducted in the Gulf of Aden, a region where phytoplankton has remained understudied. Using an integrated approach combining classical morphology and molecular phylogeny, we provide robust evidence for the presence of this species in the Indian Ocean. Morphological analyses of the isolate DJ-I1 from the Gulf of Aden reveal a typical thecal structure (plate formula: Po, pc, 5′, 0a, 9″, 9c, 8s, 9‴, 1p, 3″″) along with a characteristic lenticular shape. Although the measured cell dimensions (37–58 μm in length) are slightly smaller than those reported from other oceanic regions, the diagnostic features, including the ventral pore, apical pore, and plate arrangement, remain consistent. From a molecular perspective, LSU rDNA and ITS sequences place the DJ-I1 isolate from the western Indian Ocean within a well-supported clade comprising Pacific populations, confirming the taxonomic stability of the species despite its broad biogeographical distribution. This 10-month study also suggests that the species may be primarily associated with winter conditions. Peak abundances were observed in February, coinciding with sea surface temperatures below 30 °C and salinity below 37. These findings suggest that P. horologium may be associated with a specific range of environmental conditions in this oligotrophic environment, where its mixotrophic capacity may contribute to its persistence under these conditions.
An intra–uterine study on number of embryo in left, right and both were carried out on three species of sharks, Rhizoprinodon acutus, R. oligolinx, Carcharhinus macloti and two species of skates Rhinobatus annandalei and Rhyncobatus djiddensis. Further, intra-uterine output was examined refrence to the size of pregnant females, number of embryos, their mean lengths and size difference within and between litters in inclusion to gestation stages and the sex ratio in the shark species R. acutus, R. oligolinx, C. sorrah and Iago omanensis in rays Amphotistis imbricate, Gymnura micrura, and G. poecilura and in skates R. annandalei and R. djiddensis. The range of pup number and their mean in the litter in R. acutus was 1–4 (mean, 2.9), R. oligolinx 2–7 (3.8), C. macloti 1–3 (2.2), G. micrura, 2–3 (2.5), G. poecilura, 3–4(3.5), R. annandalei, 7–17 (10.6) and R. djiddensis 4–10 (7.2) which showed lower number of pups than the highest number of intra-uterine embryos. Interestingly, ovaries of three mature female of R. djiddensis showed an average of 14.3 ova (range, 9–18 ova) distributed equally in left and right ovaries. Therefore, taking a clue from R. djiddensis the variation observed in the number of pups in left and right uteri of the above mention species is attributed to abortion of embryos and unfertilized egg. In R. acutus, R. oligolinx, C. sorrah, I. omanensis, A. imbricate, G. micrura, G. poecilura, R. annundalie and R. djiddensis the sex ratio of embryos in embryonic condition was not statistically significant. But in the adults caught by bottom trawlers, the sex ratio was in favour of females which suggest that they segregate. Further studies on intra-uterine condition would strengthen the result of present investigation.
A study was conducted on juvenile Rachycentron canadum (cobia) fingerlings to evaluate physiological and tissue responses during post-transport retention in oxygenated packets after 24 h transportation at a packing density of 40 kg m⁻³. Post-transport retention up to 28 h was non-lethal across the treatments 24 h, 26 h and 28 h. Water quality showed gradual changes, with dissolved oxygen decreasing slightly (7.23 ± 0.09 to 7.02 ± 0.54 ppm), carbon dioxide increasing (24.16 ± 2.07 to 29.66 ± 0.89 ppm), and ammonia rising marginally (0.002 ± 0.0003 to 0.003 ± 0.0003 ppm) during the retention. Physiological stress indicators increased markedly (p < 0.05) between 24 and 28 h, as evidenced by elevated serum cortisol and alanine aminotransferase (ALT) levels. Antioxidant defense mechanisms were activated, with gill catalase activity increasing from 0.49 ± 0.05 to 1.17 ± 0.09 U mg⁻¹ protein, and superoxide dismutase (SOD) activity rising significantly in both gill tissues. Liver ALT levels increased substantially (p < 0.05), indicating hepatic stress. Histological alterations in the gills became more pronounced with increasing transportation duration. The observed enlargement of pavement cells and chloride cells associated in the ultrastructure studies indicated gill morphology alterations. Although survival was unaffected, post-transportation retention in packets induced significant physiological stress and gill alterations, highlighting the need for immediate stocking of cobia juveniles for mariculture purpose.
A mass beach stranding of the blue button jellyfish (Porpita porpita) was observed on 17 April 2025 along the Gopalpur Coast, north-western Bay of Bengal. This descriptive case study documents the event and the environmental conditions associated with it. Semi-quantitative field estimates indicated patchy deposits along about 1 km of shoreline, with a mean density of about 5 colonies m− 2. Satellite-derived datasets on sea surface temperature (SST), chlorophyll-a (chl-a), wind, currents, and salinity were examined for 1–17 April 2025. Persistent southwesterly to southerly winds (4–10 m s− 1) weakened in the second week and strengthened again before the event. A northward coastal current (0.3–1.4 m s− 1) prevailed over the shelf. Relative to the local coastline, these fields combined a dominant alongshore component with a weaker onshore component, consistent with the passive drift of P. porpita colonies towards the coast. SST near Gopalpur rose from 28.6 to 29.2 °C, within the 28–30 °C range reported for earlier strandings. SST was 0.1–1.3 °C above the decadal climatology of 2015–2024, with the largest anomaly in early April and near-climatological values on the stranding day. Nearshore chl-a often exceeded 1 mg m− 3, indicating enhanced productivity and prey availability. Pelagic barnacles were frequently attached to the stranded P. porpita. Post-stranding decomposition of colonies produced a strong odour and temporarily disrupted tourism and recreational activities. These conditions resemble those of earlier strandings on the Odisha coast but are also typical of the pre-monsoon season. The findings illustrate how physical forcing, thermal conditions, and biological productivity were associated with this stranding event and underscore the need for early warning systems along the Indian coast. Long-term monitoring of these variables, supported by nearshore observations, is needed before such events can be reliably anticipated.
