The present study reports 140 species of reef associated fishes belonging to 87 genera and 52 families and 20 orders from Mandapm, Keelakarai, Tuticorin and Vember group of islands of Gulf of Mannar Biosphere Reserve. The survey was done in the four groups of islands of the Marine National Park during December 2018 to March 2020 to assess the reef associated fishes. This study deals with the systematic and distributional list of the recorded species and description two species namely, Epinephelus magniscuttis Postel, Fourmanoir & Gueze, 1963 (Family-Epinephelidae) and Callionymus megastomus Fricke, 1982 (Family- Callionymidae) as the first record from the Gulf of Mannar Biosphere Reserve, Tamil Nadu, India. This finding represent two first records to the ichthyofaunal diversity of Tamil Nadu, India.

New record, Reef fishes, Gulf of Mannar, South east coast. 

Reef fishes are the integral part of coral reef ecosystem as they play major role in ecological balance. Fish communities are a major resource of coral reef. They play an important role in coral reef environment and are commercially important for both fisheries and more recently tourism.  Decline in the abundance of coral reef associated fish due to coral bleaching in 1998 was reported by Kumaraguru et al. (2003). Coral reefs and the associated reef fishes of Gulf of Mannar have been severely damaged due to the rampant coral mining which was happening until 2004 (Edward et al., 2008). Gulf of Mannar one of the leading producers of marine fishes in the country, however, the effect of increased fishing pressure on the resources with increasing demand and modernization of fishing practices have resulted in a decrease in the catches of several highly valued resources (Asha et al., 2009). First report of the finfish species from Gulf of Mannar (GOM) was during 1964 and contains a list of 265 fishes from GOM (Murty, 1969). Varghese et al. (2011) recorded 183 species belonging to 51 families after 4 years of study (June 2006 to November, 2010) from Gulf of Mannar. Yogesh et al. (2013) studied diversity of reef fishes in Thoothukudi and Vembar group of islands in Gulf of Mannar Islands, India and recorded 117 species under 79 genera, 42 families. Mathews et al. (2015) studied reef fishes in Tuticorin group of islands, Gulf of Mannar, South eastern India. Padate et al. (2017) reported distributional record of marine fishes from the coral reefs and deep waters of Gulf of Mannar, India. Varghese, et al. (2017) studied the diversity of reef fishes in trap fishery at Keelakarai, Gulf of Mannar, south-east coast of India. Kumar et al. (2017) studied status of corals and fishes in a deeper reef patch of Gulf of Mannar. Ammaiappan et al. (2022) reported 102 reef fishes from Kilakarai landing centre of Gulf of Mannar. Kar et al. (2022) reviewed comprehensive account of coral-reef associated fishes around the waters of the Indian subcontinent and 2,810 species were recorded from 176 families. Though some works are available on reef fish biodiversity from Gulf of Mannar a detailed list of reef fishes is lacking. So, the present study was done to documenting the reef associated fish fauna covering all four island groups of Gulf of Mannar Biosphere Reserve, Tamil Nadu.

A. Study area

The Gulf of Mannar lies between India and Sri Lanka. It encompasses the territorial waters of the southeast coast of India, from Dhanushkodi in the north to Kanyakumari in the south. This Biosphere reserve includes several ecosystems such as coral reefs, rocky shores, sandy beaches, mud flats, seaweeds, sea grasses and mangroves, each having its own zonation pattern supporting its own characteristic communities. It has a chain of 21 islands, with each island having an area of 0.5 ha minimum and 129 ha maximum. They are located 2 to 10 km from the mainland along the 140 km stretch between Tuticorin and Rameswaram (Lat 8°55′-9°15′N and Long 78°0′-79°16′E). They have fringing coral reefs and patch reefs rising from shallow areas of sea-shore. Fringing reefs are located mostly at a distance of 50 - 100 m from the islands and are narrow. These coral reefs have a rich variety of food fishes and ornamental fishes of various dimensions, colors and designs. The islands in the Gulf of Mannar are classified into four major groups viz, Mandapam group, Keelakarai group, Tuticorin group and Vembar group.

Mandapam group (seven islands): Musal, Manoli, Manoliputti, Poomarichan, Pullivasal, Krusadai, and Shingle.

Keelakarai group (seven islands): Yaanaipar, Vallimunai, Poovarasanputti, Appa, Thalaiyari, Vaalai, and Mulli.

Thoothukudi group (four islands): Van, Koswari, Kariyachalli, and Velanguchalli

Vembar group (three islands): Upputhanni, Pulivinichalli, and Nallathanni

Methodology: The four surveys were made during December 2018 to March 2020, on the reefs surrounding the Thalayari, Appa, Mulli, Vaalai, Valimunai and Anaipar Islands of Keelakarai group; Shingle, Krusadai, Hare, Manoli, Pullivasal, and Poomarichan, Island of Mandapam group; Vaan, Kasuwar, Valinguchalli and Karayichalli of Tuticorin group and Nallathanni and Upputhanni of Vembar group and landing centres nearby Gulf of Mannar Marine Biosphere Reserve (GoMBR) (Fig. 1). The specimens were observed through snorkelling diving methods; depth ranges of from 1- 4 m waters encountered especially underneath dead coral plates and exposed reef areas.  Underwater photographs were taken in situ to record the fish specimens present in the coral reef habitat. Digitization of individual species was made by underwater camera (NIKON, Model-COOLPIX W300, 16.05 megapixels). Fish specimens from the intertidal zones of the islands were collected by using hand nets. Hiring artisanal craft and application of practicing gears were applied for collection and observation of fish specimens. Some specimens were collected from the landing centres in and around Gulf of Mannar regions. Co-ordinates of the sampling areas were obtained using GPS (GARMIN GPS map 78S). The collected fishes were photographed in the field and then fixed in 10% formalin solution. The specimens were identified up to species level following standard publications for identification of fishes is Fischer and Bianchi (1984); Talwar and Kacker (1984); Smith and Heemstra (1986); Rao (2004). Underwater photo of fishes were identified up to species level following Randall et al. (1998); Lieske and Myers (1996); Allen et al. (2005);  Rajan (2010);  Kumar et al. (2012). The taxonomy followed in the manuscript is based on FishBase (Froese and Pauly, 2025) and the Catalogue of Fishes (Eschmeyer, 2024). The specimens collected and identified were deposited in the collections of National Zoological Collections of Marine Biology Regional Centre, Zoological Survey of India, Chennai.

A total of 448 specimens with underwater photographs of fishes were collected during the survey period (December 2018 to March, 2020) from the Mandapm, Keelakarai, Tuticorin and Vember groups of islands including landing centres in and around Gulf of Mannar region. From the collected specimens and underwater photographs, 140 species were identified belonging to 87 genera, 52 families and 20 orders. The checklist of the species with distribution in four different island groups of from Gulf of Mannar Biosphere Reserve has been presented in Table 1. The species inventory also registered four species of fishes belonging four different families reported for the first time from Gulf of Mannar region i.e Asterropteryx semipunctata Ruppell, 1830 (Family-Gobiidae), Pseudamia gelatinosa Smith 1956 (Family-Apogonidae), Epinephelus magniscuttis Postel, Fourmanoir & Gueze, 1963 (Family- Epinephelidae) and Callionymus megastomus Fricke, 1982 (Family-Callionymidae). The two species namely Epinephelus magniscuttis and Callionymus megastomus has been described in this paper as former two are already described.  

Taxonomic Account  

Class: Actinopterygii

Order: Perciformes 

Family: Epinephelidae

Genus: Epinephelus Bloch, 1793 

1. Epinephelus magniscuttis Postel, Fourmanoir and Gueze, 1963

Speckled Grouper (Fig. 2)

1963. Epinephelus magniscuttis Postel, Fourmanoir and Guézé: 365, fig. 9 (Type locality: Reunion).

Material examined: MBRC/ZSI/ F.2456, 1 ex., 92.6 mm SL. 04.iii.2020, Valinokkam.

Diagnostic characters: D: XI, 15; A: III, 8; P: 18; V: I, 5. Body elongated with large mouth. Body depth 3.2 times to standard length (SL), Head profile straight covered with minute scales. Head length (HL) 2.23 times to SL; Eye moderate 5.2 times in HL. Interorbital area flat, peropercle angular, upper part finely serrated and angle with 3 large serrae. Gill rakers 8 on upper limb,16 on lower limb. Operculum with three spines, middle one pointed, situated midway between upper and lower spines. Dorsal fin single, continuous, interspinous membrane incised; pelvic fin not reaching to anus, caudal fin rounded.

Colour: Pale brown with small round black spots distributed irregularly in mid lateral part of head and body; Paired fins, anal fin and ventral part of body & head are devoid of spots. Upper margin of maxillary groove is dark brown; three dark bands originating from posterior margin of orbit. Dorsal dark brown; Pectoral, pelvic, anal and caudal light brown at the base and dark towards edges (Fig. 2). 

Distribution: Indo-West Pacific (Heemstra & Randall 1993). From Indian coast, this species has been reported from Andhra Pradesh (Sujata et al., 2015), West Bengal (Ray & Mohapatra 2022) and Odisha coast (Sahoo et al., 2020).  This paper adds its distribution to Gulf of Mannar, Tamil Nadu which further extends the range in southeast coast of India. 

Taxonomic account

Class: Actinopterygii 

Order: Callionymiformes

Family: Callionymidae Bonaparte, 1831

Genus: Callionymus Linnaeus, 1758

2. Callionymus megastomus Fricke, 1982

 Indian megamouth dragonet (Fig. 3)

1982. Callionymus megastomus, Fricke, J. Nat Hist. 16:345, Fig. 1 ; (Type locality: Calcutta, India).

Material examined: MBRC/ZSI/ F.2434, 1 ex., 72.4 mm SL. 04.iii.2020, Valinokkam.

Diagnostic characters: D1  III ; D2 I, ix  ;  A viii,  P 14 ,  V  I, 5;  C i, 7.

Body elongated and depressed. Head depressed its length 4.2 in standard length. Body depth 10.7 in standard length.Body width 3.9 in SL. Eye large, 3.23 in head length.preorbital length 3.4 in HL. Interorbital distance 4.6 in eye diameter. Branchial opening dorsal in position. Upper jaw highly protruding. Main tip of preopercular spine curved upward, angular, one antrose spine at preopercular spine base and three curved serrae at its dorsal margin. Urogenital papilla elongated.  First dorsal fin is higher than second dorsal fin. Pectoral fin long, reaching to base of second anal-fin ray; pelvic fin distally conex, does not reaching the base of first anal fin. Distal margin of caudal fin is convex.

Colour: Body brown, head light brown with darker cheeks and a number of darkish lateral spots dorsally, turning whitish-yellow ventrally. Eye dark brown, belly whitish.  Dorsum with numerous small dark brown spots. First dorsal fin is brown, Pelvic fin translucent with two dark spots. Middle of the caudal fin with many irregular dark spots.

Distribution: This species is known only from Gulf of Bengal, off Calcutta, India (Fricke, 1982). The present report extends geographic distribution of C. megastomus to Gulf of Mannar Biosphere Reserve, south east coast of India. 

In the present study, 140 species of reef associated fish species were identified belonging to 87 genera, 52 families and 19 orders with first distributional records of four species of fishes from Gulf of Mannar ecosystem. The species Asterropteryx semipunctata Ruppell, 1830 was previously reported from Lakshadweep and Andaman Islands. Pseudamia gelatinosa Smith 1956 was reported only from Lakshadweep (India); Epinephelus magniscuttis Postel, Fourmanoir & Gueze, 1963 previously reported from Andhra Pradesh, West Bengal and Odisha coast only. Callionymus megastomus Fricke, 1982 previously reported only from Kolkata, Bay of Bengal, India. Baiju et al. (2024) recorded 232 fish species from the rocky reef areas of Kerala coast, southwest coast of India among them 31 species extended new distribution ranges within the Indian Ocean and India. From the distribution of identified fishes in four groups of islands of Gulf of Mannar it was observed that highest numbers of fishes were recorded from Mandapam group of islands followed by Keelakarai group of islands, Tuticorin group of islands and Vember group of islands respectively. The identified fishes belonging to 52 families were most diverse recorded during this study. The number of species in the largest group  that belong to the family Lutjanidae, Apogonidae, Chaetodontidae followed by Labridae, Pomacentridae, Serranidae, Lethrinidae, Haemulidae, Acanthuridae, Mullidae and Terapontidae. The reef fishes are diverse and abundance in the area surveyed. 

Table 1: List of reef fishes recorded from Gulf of Mannar, Tamil Nadu.

    ‘+’ present/recorded;   ‘-’ absent /not recorded

Fig. 1. Map showing sampling sites in Gulf of Mannar, Tamil Nadu, India.

Fig. 2. Epinephelus magniscuttis Postel, Fourmanoir & Gueze, 196.

Fig. 3. Callionymus megastomus Fricke, 1982.

From the study of the reef associated fishes, it is evident that Gulf of Mannar has a good coral cover with high fish density. Reef fishes are important to many processes occurring in the reef and loss would affect the health of the coral reef ecosystem. The degradation of the coral reef habitat, overharvesting, industrialization is leading to heavy losses in reef diversity around the globe, so the study is important and significant in this line, which could form a baseline data for future workers in fish and fisheries. 

Mrinal Kumar Das  (2026). A Study on Reef Fishes of Gulf of Mannar Biosphere Reserve, Southeast Coast of India with New Records. Biological Forum, 18(2): 07-17.