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A new species of deep-water snake eel, Ophichthus nigroventralis sp. nov. is described based on five specimens collected from deep-sea trawl landings at Kalamukku fish landing Centre, off Kochi, Arabian Sea, southwest coast of India. The new species is distinguished from its deep-water congeners by the following combination of characters viz., origin of dorsal fin slightly behind pectoral-fin tip; pectoral fin lanceolate, slightly shorter than upper jaw in length; head length 6.7–7.5 in TL; supraorbital (SO) pores 1 + 3; intermaxillary with a rosette of 10 pointed teeth; vomer with 6 anterior teeth in irregular biserial rows, 11 posterior teeth in a uniserial row; maxillary with 24–25 uniserial teeth; abdomen with numerous minute black pigmentation extends up to tail; pectoral fin whitish with brown base; vertebral count (pre-dorsal/pre-anal/total): 17–18/53–54/131–134. The genetic analysis reveals that the species Ophichthus urolophus is the closest congener for the new species with a genetic divergence of 4.2%.

Ariosoma albimaculata sp. nov. is described herein based on ten specimens [240–487 mm total length (TL)] collected from the deep-sea trawl landings at Colachel fishing harbour, off Kanyakumari, Arabian Sea, west coast of India. The new species is easily distinguished from all other congeners reported earlier, except its sympatric species, Ariosoma maurostigma Kodeeswaran, Mohapatra, Dhinakaran, Kumar and Lal 2022, having dark mark or streak present in the posterior-dorsal margin of eye orbit, but it readily differs from A. maurostigma with the presence of more total vertebrae (161–164 vs. 136–142 in A. maurostigma ); more preanal vertebrae (66–68 vs. 47–51); occurrence of white spot or dot on just before the dorsal-fin origin (vs. absent in A. maurostigma ); larger preanal length (49.7–55.7% TL vs. 44.0–48.8% TL); larger trunk length (30.4–33.3% TL vs. 23.5–30.2% TL); shorter tail length (44.6–48.2% TL vs. 47.8–54.6% TL). Further, A. albimaculata differs from its sister taxon A. maurostigma with a divergence of 8.1% and other congeners with the genetic distance of 15.0–28.8% in partial mitochondrial COI gene.

Two new species have been described from Indian waters, based on the materials collected from Kochi coast, Arabian Sea, Gulf of Mannar and West Bengal coast along the Bay of Bengal. Ariosoma gracile sp. nov. is described, based on five specimens collected from the landings at Kalamukku Fishing Harbour, Arabian Sea. The new species is characterised by longer tail, 55.3–58.7% TL; dorsal-fin origin above pectoral-fin base; no dark or whitish bands on dorsal surface of head, ventral extremities of lower jaw and mid-portion with minute dark pigmentation patch; anus positioned well before the middle of total length; SO canal with 4 pores; 0 or 3 pores on ST canal; pre-dorsal vertebrae 9; pre-anal vertebrae 49–54; total vertebrae 140–142. Ariosoma gracile sp. nov. is closely related to Ariosoma dolichopterum and Ariosoma emmae by sharing similar morphometrics and pre-anal vertebral counts. However, it differs by having more total pores (132–135 vs. 121–129 in A. dolichopterum , 123–126 in A. emmae ); fewer pre-anal pores (43–46 vs. 47–51 in A. dolichopterum , 50–53 in A. emmae ); more pre-dorsal pores (9 vs. 5–9 in A. dolichopterum , 4–6 in A. emmae ). Another new species, Ariosoma kannani sp. nov. is described on the basis of two specimens (157–171 mm TL) from Gulf of Mannar and one specimen (201 mm TL) collected from Shankarpur Fish Landing Centre, West Bengal. This species is similar to Ariosoma megalops , but readily differs by having smaller eyes, smaller interorbital distance and exhibits 10.8% genetic divergence from A. megalops from the Taiwan waters.

The Bearded Ghoul, Inimicus didactylus (Pallas, 1769), a member of stonefish family previously known to be distributed only in the western Pacific from southern Japan, northern Australia and Vanuatu is reported herein from the southeast coast of India. This report constitutes the fifth species of the genus Inimicus to be reported from the Indian waters. The meristic and morphological characters of I. didactylus recorded in the present study is compared with I. sinensis , a species commonly distributed in the east coast of India.

The Canarytop Wrasse, Halichoeres leucoxanthus Randall & Smith 1982 , previously distributed from Maldives, Myanmar, Christmas Island (Australia), Thailand and Western Indonesia was recorded for the first time from Indian waters on the basis of six specimens (measures 53.1–66.3 mm SL) collected from the Gulf of Mannar, East coast of India. The species was diagnosed with the bicoloured body, striking yellow dorsally and milky white ventrally; three dark or black spots on the dorsal fin; a single black spot located mid-laterally on the fifth branched ray towards the basal region of the caudal fin. The partial mitochondrial COI gene of H. leucoxanthus was generated and the genetic analysis reveals that, H. leucoxanthus was closely related to Halichoeres chrysus Randall 1981 and Halichoeres iridis Randall & Smith 1982 with a genetic distance of 7.2% and 6.4%, respectively. The present study reports the range extension of H. leucoxanthus in Indian waters based on meristic, morphometric and phylogenetic details.

The present study provides notes on Cocotropus roseus Day, 1875, a poorly known endemic fish from the Bay of Bengal, Eastern Indian Ocean. The morphometric data and color images are provided herein based on fresh specimens collected from Chennai, south India, its type locality, Bay of Bengal, Eastern Indian Ocean.

A new species of the genus Pangasius, is described based on 17 specimens collected from the Cauvery River, India. It can be distinguished from its sister species from South and Southeast Asia, by its widely placed, small and rounded vomerine and palatine tooth plates, longer maxillary and mandibular barbels, greater vertebrae count 50 (vs. 44–48), and smaller caudal peduncle depth (6.5–8.2% SL vs. 9.89–13.09% SL). The tooth plates of the new species closely resembles that of Pangasius macronema but can be clearly distinguished from the latter by having lesser gill rakers (16–19 vs. 36–45); a smaller eye (2.4–4.4% SL vs. 5.2–9.6% SL); and larger adipose-fin base (1.5–2.9% SL vs. 0.1–1.2% SL). The mitochondrial cytochrome c oxidase (COI) gene sequence of the new species shows the genetic divergence of 3.5% and 5.1% from P. pangasius and P. silasi respectively, the two sister species found in South Asia and India. The species delimitation approaches, Poisson Tree Processes (PTP) and assemble species by automatic partitioning (ASAP) clearly resolved that the P . icaria is distinct from its sister species. Phylogenetic position of the species with its sister species was evaluated using maximum likelihood and Bayesian analysis. The discovery of this previously unknown species of genus Pangasius from the Cauvery River of peninsular India indicates important biogeographical insight that this genus migrated till the southern division of Western Ghats.

Gymnothorax tamilnaduensis sp. nov. , a new species of short brown unpatterned moray, is described, based on four specimens ranging from 272–487 mm total length collected from the trawl bycatch landings at Mudasalodai fish landing centre, off Cuddalore coast, Tamil Nadu, southeast coast of India. The new species is distinguished by the following combination of characters: origin of dorsal fin at middle of rictus and gill opening, anus just before mid-body, series of lines of small dark spots present on head and a single line of black spot-on mid-line of body, jaw pores with white rim, anal-fin margin whitish, 3 pre-dorsal vertebrae, 56–59 pre-anal vertebrae and 139–150 total vertebrae. The new species differs from its known Indian water congeners by having series of lines of small dark spots present on the head and a single line of black spots on the mid-line of the body (vs. absent in all the three congeners in India), serrated teeth (vs. smooth), jaw pores with white rim (vs. black to brown in others) and higher vertebral count (139–150 vs. 134–138 in others). Our morphological and molecular analyses show that the new species forms a distinct clade from its congeners and these data support the status as a new species.

A shrimp-associated goby, Myersina yangii (Chen, 1960), is reported from the east coast of India, based on a single specimen. It measured 61.16 mm in standard length. This finding represents the second record of the genus Myersina and the first record of M. yangii from Indian waters. The species is discussed herein with its meristic and morphometric characteristics.

A new species of congrid eel genus, Ariosoma is described here based on two mature female specimens collected from trawl by-catch landings at Thoothukudi fishing harbour, off Thoothukudi, Bay of Bengal. The new species can be easily distinguished from its congeners in having pre-anal length 48.7–49.1% TL; dorsal-fin origin just before pectoral-fin insertion; body bicoloured, pale brown dorsally and silvery white ventrally; preopercular portion dark; pectoral fin reddish with dark spot at the base; SO canal with six pores; pre-dorsal vertebrae 10–11; pre-anal vertebrae 61–64; total vertebrae 162–163. Further, the new species differs from all the congeners of Indian waters in having more total vertebrae, except A. albimaculatum (162–163 vs 129–153 in others; 161–164 in A. albimaculatum). The new species identity was also supported by molecular analyses using the mitochondrial COI gene and the result revealed that the new species is closely related to Ariosoma maurostigma and Ariosoma albimaculatum with a pair-wise genetic distance of 11.4% and 11.6% followed by A. melanospilos with 16.8%.