Abstract:
The coral reefs and deep water ecosystems of Gulf of Mannar support diverse assemblages of marine fishes vulnerable to indiscriminate mechanized fishing. However, lack of comprehensive information on the fish diversity of these ecosystems is aggravated by the habitat complexity of the fishing grounds, inadequate faunistic surveys and insufficient taxonomic expertise. In view of this, the present paper aims to document rare fishes and supplement the existing species inventory from this region. Sampling surveys included 23 hauls on-board commercial single-day otter trawlers operating bottom trawls at 15-100 m depths, and mid-water trawls at 100-153 m depths in the Gulf of Mannar. In addition, by-catch landings of commercial trawlers were surveyed at Tuticorin fishing harbour. Specimens were subjected to morphometric and meristic examination and deposited at the Central Marine Fisheries Research Institute, Kochi. The presently reported survey of rare fishes revealed one elasmobranch, Hypogaleus hyugaensis (Miyosi, 1939). In addition, 12 species of teleosts belonging to four orders, 10 families, and 11 genera were identified as Uropterygius micropterus (Bleeker, 1852); Dendrochirus bellus (Jordan et Hubbs, 1925); Snyderina guentheri (Boulenger, 1889); Acropoma japonicum Günther, 1859; Gymnocranius elongatus Senta, 1973; Pomacentrus similis Allen, 1991; Pristotis cyanostigma Rüppell, 1838; Leptojulis cyanopleura (Bleeker, 1853); Naso annulatus (Quoy et Gaimard, 1825); Naso thynnoides (Cuvier, 1829); Pseudalutarius nasicornis (Temminck et Schlegel, 1850); and Lagocephalus suezensis Clark et Gohar, 1953. The present paper provides descriptions of each species supplemented with meristic counts and morphometric measurements. An identification key to these species is provided. Hypogaleus hyugaensis, U. micropterus, D. bellus, P. cyanostigma, N. thynnoides, P. nasicornis, and L. suezensis represent the first records in Indian waters. Additionally, G. elongatus, P. similis, and N. annulatus represent the first records off the Indian mainland, and S. guentheri, A. japonicum, and L. cyanopleura represent the first records off the East coast of India. Among these, D. bellus, S. guentheri, and P. cyanostigma represent the first records outside their known zoogeographical ranges. Patchy zoogeographical distribution and extension of known geographical ranges are attributed to recurrence of vicariance events in the geological past.
