Occurrences of immortal jellyfish Turritopsis cf. dohrnii from the Mandapam coastal waters of the Gulf of Mannar

During the routine jelly plankton survey along the Mandapam coastal waters, a swarm of hydrozoans was collected in February 2022. These were identified as the immortal jellyfish Turritopsis cf. dohrnii. The hydrozoan jellyfish swarm is the medusa stage of the organism, whereas the larval phase is sedentary and attached to some hard substratum at the bottom. Once a larva metamorphoses into a polyp, it buds off as a jellyfish, causing a bloom

Seagrass, Seaweed and Mangrove ecosystem of Gulf of Mannar and Palk Bay region

The Gulf of Mannar, a shallow bay, with a coastline of 364.9 km, is known for its coral reefs and sea grass beds which harbour several endangered species. The Gulf-of-Mannar Marine National Park (GOMMNP) declared in 1986, under the Wildlife (Protection) Act, 1972, covers an area of almost 560 sq. km andincludes 21 islands. The 21 islands are distributed in four groups – Mandapam, Keezhakarai, Vembar and Tuticorin groups and located in 3-6 miles distance from the coast and vary in area from 0.25 ha to 130 ha.The Gulf of Mannar, the first Marine Biosphere Reserve (GOMMBR) in the South and South East Asia, covers from Rameswaram to Kanyakumari in Tamil Nadu, Indi

First record of deformity in Chinese Pomfret, Pampus chinensis (Euphrasen, 1788) from Indian waters

The Chinese pomfret Pampus chinensis (Euphrasen, 1788) (Stromateidae) observed with deformity from fish landings at the Jegathapattinam fishing harbour along Palk Bay coast of Tamil Nadu. The abnormality owing to fractional dorsal fin may call as ‘saddleback syndrome’ and this may be due to any kind of physical injury during early stages or to a higher chance of predation and in due course, the wound healed and the individual survive even with extreme deformed condition. Such a deformity for this species of Pomfret has never been documented from Indian waters and this could be the first record in Pampus chinensis

Impact of mini trawl fishing on the population of alligator pipefish Syngnathoides biaculeatus bloch (1785) caught as bycatch from the seagrass meadows of Palk bay, southeast coast of India

Seagrass meadows are a highly productive ecosystem providing habitat, breeding and feeding ground for various marine species and also support the fisheries. The single species S. biaculeatus is the most dominant pipefish among Syngnathoids in Palk Bay. Periodic monitoring and observation of bycatch and discards, of the alligator pipefish Syngnathoides biaculeatus, caught in Mini trawl from Devipattinam for one year formed the basis of this communication. The size range of alligator pipefish was recorded between 128 mm to 240 mm and individual weight ranged from 1.42 to 6.60 g. The maximum numbers of Pipefish were recorded during July 2017. There is no significant difference in b values (P > 0.05) and K values between male and female. In the present study, population of pipefish S. biaculeatus have shown negative allometric growth pattern (b = 1.92). Fishing by Mini trawl in the inshore region of seagrass meadows has harshly affected the alligator pipefish population and its habitat. Mesh size regulation and its strict implementation will be the required management measures to ensure the sustainability of the pipefish population in the seagrass meadows of the Palk Ba

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay off Coromandel Coast, south India

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay, off Coromandel Coast, south India, were computed from the organic carbon content and dry bulk densities of sediment core taken from the seagrass meadows of these two ecosystems. The Gulf of Mannar (GoM) and Palk Bay (PB) harbour 13 seagrass species dominated by Cymodocea serrulata and Syringodium isoetifolium. The soil carbon density of both GoM and PB were higher in subsurface cores

First record of deformity in Chinese Pomfret, Pampus chinensis (Euphrasen, 1788) from Indian waters

The Chinese pomfret Pampus chinensis (Euphrasen, 1788) (Stromateidae) observed with deformity from fish landings at the Jegathapattinam fishing harbour along Palk Bay coast of Tamil Nadu. The abnormality owing to fractional dorsal fin may call as ‘saddleback syndrome’ and this may be due to any kind of physical injury during early stages or to a higher chance of predation and in due course, the wound healed and the individual survive even with extreme deformed condition. Such a deformity for this species of Pomfret has never been documented from Indian waters and this could be the first record in Pampus chinensis

Seasonal variability in the distribution of microplastics in the coastal ecosystems and in some commercially important fishes of the Gulf of Mannar and Palk Bay, Southeast coast of India

Impact of microplastic pollution on the marine environment and its biota is a major concern globally. Gulf of Mannar (GoM) and Palk Bay (PB) are two important biodiversity hotspots along the south-east coast of India. However, in the recent years the intense tourism and fishery activities have made the ecosystem and biota of these two ecologically significant coastal zones vulnerable to microplastic contamination. Hence, a comparative study on the seasonal distribution of microplastics in the surface waters, sediments, and in commercially important fishes were conducted to evaluate the threats imposed by microplastics on the environment and biota of both these coastal ecosystems. Microplastic distribution in the surface waters and sediments of GoM and PB exhibited conspicuous seasonal variation and showed positive correlation with the seasonal current patterns. In the surface waters of GoM, microplastics were abundant during the South West Monsoon whereas in PB it was high during the Early Winter Monsoon period. In the sediments of PB, microplastics was more during Spring Inter-monsoonand South West Monsoon whereas in GoM it was high during Late Winter Monsoon. Fragments, of size 1 to 5 mm formed the abundant microplastic type in the surface waters whereas in the sediments, fragments of size < 1 mm dominated. Of the gut content of the 613 fishes belonging to 12 families examined, microplastics were more in pelagic than demersal fishes with higher incidences in the family Clupeidae (42%). Among the fishes studied, microplastic ingestion was more in Selaroides leptolepis (27.77%), Sphyraena sp. (14.28%), Pelates quadrilineatus (12%), Caranx sp. (10.34%), and Sphyraena barracuda (10%)

Note on mass mortality of Bloch’s gizzard shad at Dhanushkodi lagoon, Tamil Nadu

Mass mortality of Bloch’s gizzard shad, Nematalosa nasus (Bloch, 1795) was observed around 5 km shore area of the lagoon from Ottathalai to Thavukadu near near the Kothandaramar Temple, Dhanushkodi, Ramanathapuram District, Tamil Nadu on 19th October 2019. An estimated 3 tonnes of Nematalosa nasus were washed ashore and water samples collected from the site were analysed indicated Dissolved oxygen (2.17ppm), pH (7.83ppm), salinity (40ppt), temperature (30.6oC), ammonia, nitrite and nitrate (0.1, 0.2 and 0.43 ppm respectively)

Monitoring of Harmful Algal Bloom (HAB) of Noctiluca scintillans (Macartney) along the Gulf of Mannar, India using in-situ and satellite observations and its impact on wild and maricultured finfishes

In the Gulf of Mannar, Noctiluca scintillans blooms have been observed three times in September 2019, September and October 2020, and October 2021. It was determined and measured how the bloom period affects ichthyo-diversity. Noctiluca cell density varied slightly from year to year, ranging from1.8433 × 103 cells/L to 1.3824 x 106cells/L. In surface and sea bottom waters, high ammonia levels and low dissolved oxygen levels were noted. During the bloom period a significant increase in chlorophyll concentration was found. The amount of chlorophyll in GOM was extremely high, according to remote sensing photos made using MODIS-Aqua 4 km data. Acute hypoxia caused the death of wild fish near coral reefs and also in fish reared in sea cages. The decay of the bloom resulted in significant ammonia production, a dramatic drop in the amount of dissolved oxygen in the water, and ultimately stress, shock, and mass mortality of fishes