ISSN 0375-1511 Rec. zool. Surv. India: 113(Part-3): 59-77, 2013 MANGROVE ASSOCIATE GOBlES (TELEOSTEI: GOBIOIDEI) OF INDIAN SUNDARBANS T. K. CHATTERJEE~ R. P. BARMAN2AND s. s. MISHRA4 'Zoological Survey of India, Sundarban Field Research Station, Canning 2Zoological Survey of India, Marine Fish Section, Kolkata *E-mail: [email protected] INTRODUCTION Our knowledge of these fishes of Bengal (pre­ The gobioid fishes are distributed throughout partitioned) dates from Hamilton (1822) who described 16 gobioid species from the lower the temperate and tropical zones of the world. reaches of the River Ganga. Later, Annandale They occur in fresh to hyper saline waters, in mud, (1907), Hora (1933, 1935 a, b), and others sand as well as reef habitats. Some species have a contributed significantly to the fishes of Hugli­ very wide distribution, while a few are markedly Matla estuarine system. The monumental work of localized. Most species are cryptic bottom Koumans (1941) gives a vivid account of gobioid dwelling carnivores that usually feed on small fishes of India that incorporates a number of benthic invertebrates. Abundance in number of species from lower Bengal. Chatterjee (1978) species, intraspecific morphological diversity and studied the gobioid fishes of the Gangetic delta interesting habitat, behaviour and adaptations and described a new genus and new species make them a subject of great biological (Chatterjee and MIshra 2013). Talwar et al., (1992) importance. Most of the gobioid fishes found in and Mukherjee (1995) further contributed to the the Sundarbans are mangrove associates, wealth of gobioid fauna of West Bengal and the particularly the mudskippers are characteristic of Hugli-Matla estuaries. any mangrove habitat. The present study aims at giving an account The Sundarbans is known as the world's of the mangrove associate gobioid fishes of the largest mangrove ecosystem. Mangroves are well Indian Sundarbans, where inundation and known as transition from the marine to exposure occur twice in every block of 24 hours. This work incorporates the review of the gobioid freshwater and terrestrial ecosystems. They fishes occurring in the region. The current status provide critical habitat for numerous species of of species is mostly following Froese and Pauly fishes and crustaceans that are adapted to (2013) and Eschmeyer (2013). The gobiid live, reproduce and spend their juvenile lives classification in to subfamilies is in accordance among the tangled mass of roots, known as with Nelson (2006). The identification keys pneumatophores, that grow upward from the provided here are meant for Indian Sundarbans anaerobic mud to get the trees' supply of oxygen. only and that may not suitable for other However, it is difficult to say which species are geographic regions. confined to the mangroves and are not occurring in other habitats (Macnae, 1966). Hence, the total MATERIAL AND METHODS habitat is taken into consideration to study this The largest part of the material, on which the peculiar group of fish. present work is based, is housed in the National 60 Rec. zool. Surv. India Zological Collections of the Zoological Survey of ZSI Zoological Survey of India India (Z.5.I.), Kolkata. The collections include a ZSI-ASB Asiatic Society of Bengal collections, large number of gobioid fishes collected by Sir F. now housed in the Zoological Survey Day, A. W. Alcock, N. Annandale, S. L. Hora, and ofIndia, Kolkata others, which include a number of type specimens. Most of the specimens on which F. P. ZSI-SFRS Sundarban Field Research Center, Koumans based his monumental work ZSI, Canning collections (Koumans, 1941) are also preserved in the Z.5.I. The Sundarbans These specimens include several collections from The Sundarbans can be defined as a group of the adjoining areas of Sundarbans. All specimens islands starting from the mouth of river Hughly included in Mukherjee (1995), housed in Z.5.I., on the west and extending up to the river Meghna were re-examined and used for the present work. in the east, covering four districts, two from West It is also supplemented by recent collections of Bengal viz. North 24-Parganas, South 24- gobioid fishes during 2007-08 from the various Parganas districts; and two from Bangladesh, viz., locations of Sundarbans. The study area is shown Khulna and Barishal districts. The Indian in fig.1 and a satellite picture of the Sundarbans is Sundarbans at the apex of Bay of Bengal (latitude also shown in fig.2. Recent collections were made 21°13'- 22°40' N. and longitude 88°03'- 89°06' E.) is from the following places. Garmin 12 channel located on the southern fringe of the state of West GPS was used to mark the latitude and longitude Bengal, covering the major portions of North and of the places surveyed. The places surveyed South 24-Parganas districts. The region is recently and their GPS points are as follows: bordered by Bangladesh in the east, the Hughly Gosaba 22° 09.924' N; 88° 47.819' E river in the west, Dampier-Hodges line in the north and Bay of Bengal in the south. As regards Sajnakhali 22° 07.485' N; 88° 49.809' E the total area of Sundarban forests, a number of Dobanki 21 ° 59.368' N; 88° 45.259' E estimations are found in literatures (Dey, 2006). In Haldibadi 21 ° 43.547' N; 88° 46.966' E a recent estimation by the Forest department, it has been stated that 4,264 sq. km. forest persists Chamta 21 ° 51.667' N; 88° 54.831' E within Indian Territory and 4,109 sq. km. in Khatuajhuri 22° 03.293' N; 88° 59.356' E Bangladesh. With considerable degree of marine Burirdhabri 22° 04.653' N; 89° 01.730' E characteristics in the major portion of the ecosystem, the important morphotype of the Jhila 22° 11.393' N; 88° 57.543' E deltaic Sundarbans are beaches, mudflats, coastal Neti Dhopani 21 ° 55.219' N; 88° 44.759' E dunes, sand flats, estuaries, creeks, inlets and Dobanki 22° 59.368' N; 88° 45.259' E mangrove swamps. The mangrove environment can be differentiated into four forest types, viz., Sudhanyakhali 22° 06.058' N; 88° 48.075' E Tidal Swamp Forests, Saline Water Type Mixed Basanti 22° 12.167' N; 88° 42.660' E Forests, Brackish Water Type Mixed Forests, and Jharkhali 22° 01.127' N; 88° 40.935' E Palm-Swamp Type. Though it is very difficult to define the mangrove fauna as a whole, Ekman Sonakhali 22° 12.259' N; 88° 42.655' E (1935) stated that the mangrove fauna is Canning 22° 19.184' N; 88° 40.471' E characterized by its low species diversity Abbreviations of names of the organizations used represented by large populations. Macnae (1966) in this work: observed that it is difficult to say which species are confined to the mangrove and are not occurring in SDCMBRI Susama Devi Chowdhurani Marine other habitats. On the other hand, same species Biological Research Institute, Sagar may be available in various mangrove ecosystems Island within the same ecological region. CHATTERJEE et al. : Mangrove Associate Gobies (Teleostei: Gobioidei) of Indian Sundarbans 61 Main Flora and fauna: There are 64 plant TAXONOMIC ACCOUNT species in the Sundarbans with the capacity to The suborder Gobioidei belongs to the Class withstand estuarine conditions and saline Actinopterygii (ray-finned fishes) and the Order inundation as a result of tidal effects. Some of Perciformes. Gobies are primarily marine fishes, them are listed here: Excoecaria agallocha, Heritiera also found in brackish and freshwater fomes, Ceriops decandra, Ceriops tagal, Phoenix environments. The characteristics of the gobioid paludosa, Sonneratia alba, Avicennia spp., fishes (Miller, 1973) are as follows. Body without Rhizophora apiculata, Rhizophora mucronata, lateral line canal, but with only exposed Xylocarpus granatum, Nypa fruticans, Bruguiera neuromast organs (pit organs). Head generally spp. etc. The invertebrate faunal diversity of with sensory canal-pores. Oculoscapular lateral Indian Sunderbans, as enumerated by MandaI line canal, when present, mayor may not extend and Nandi (1989), comprised one species of over snout before nostrils, preopercular canal Porifera, 5 Cnidaria, 1 Ctenophora, 5 Rotifera, 2 with 2-5 primary pores, or often absent; Nematoda, 2 Chaetognatha, 3 Ectoprocta, 1 horizontal section of preopercular canal at best Brachiopoda, 2 Echiura, 1 Sipuncula,48 Annilida, very short, distant from angle of jaw and usually about 170 Crustacea, 155 Insecta, 35 Arachnida, 94 lacking. Scales with only peripheral ctenii Mollusca, and 14 Echinodermata. In addition to consistently developed, sometimes cycloid or Royal Bengal Tiger, the vertebrate fauna comprise absent. Five to 7 branchiostegal rays. The 58 species of mammals, around 248 bird species suborder Gobioidei is grouped under nine and 55 species of reptiles as per 2004 census. families (Nelson, 2006), of which only two Although the Census report includes only 47 families are found to occur in the Sunderbans. species of fishes from the Indian part of the Sundarbans, MandaI and Nandi (1989) gives a list FAMIL Y ELEOTRIDAE of about 140 species that include only 14 species of Body elongate, scales small to moderate. Two gobioid fishes. Mangrove associate gobies are dorsal fins separate or connected only at their generally represented by aquatic and semi­ bases. First dorsal fin comprises 6 flexible spines; aquatic communities adapted at stress conditions. second with one spine and 8 or 9 rays. Anal fin Gobioids of Bangladesh Sundarban: As with one spine and 6 to 9 rays. Ventral fins there is no physical, climatic or any other natural separate either completely to the base or almost to barrier in Sundarbans between India and it. Body without lateral line canal, only exposed Bangladesh, it can be presumed that similar neuromast organs (pit organs). Head usually with composition of mangrove associate gobies are sensory canal pores.