A total of 250, 000 named marine species compared to 1.7 million known terrestrial species may be due to inadequate explorations, especially in deep seas. For example, among 156 sea fan species collected from Tamil Nadu coast, only 60 were previously identified. Out of 50 brachyuran crab species collected in Karwar, Karnataka, 37 are new to locality and at least one is new to India.
Of nearly 40 benthic polychaete species at Tamil Nadu, one third is new to India. Reef-building corals belonging to 294 species are known till date, with possible addition of another 400 species. Marine species shows lower level of endemism than terrestrial species. Among 5344 marine animal species known from Andaman and Nicobar Islands till date, only 297 (5.5%) are endemic.
Marine molluscs generally have highest level of endemism (14%) (Vencatesan, 2006) Eighty different marine habitats could be enumerated for India, of which the shallow coastal waters not exceeding a depth of 200 m are most productive. Coastal nation are rich fishing groups.
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Total commercial marine catch over last ten years at the rate between 1.4 and 1.6 million tonnes has been more or less stabilized, with clupeoid groups accounting for approximately 30% of all landings. Sea fans and seaweeds are exported for decorative purpose. Spiny lobster fishing industry along south-east coast is also notable. Indian coral reels have gained importance recently.
Reef fisheries are generally at subsistence level and yields are unrecorded. Sea grass beds are valuable habitats of prawns and mangrove stands and are important feedings areas for dugong and several marine turtle species. In the Gulf of Mannar, Penaeus semisulcatus is extensively harvested for export. Marine fishery is important for domestic demand of protein food and imperatives of exports.
An increased investment in this sector has taken place during last few years and fishing fleet has expanded rapidly. Presently, marine fishermen face difficulties in fish capture in spite of exerting the same and sometimes more effort. Thus, question of sustainability of marine fishing arises. Estimate of sustainability of marine fishing in Digha-Shankarpur coastal region show that actual yields of all varieties are still below maximum sustainable yield except few cases (Das, Neogy and Chakroborty, 2000).
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Marine turtle’s viz., Chelonia mydas, Caretta caretta, Lepidochelys olivacea, Eretmochelys imbricata and Dermochelys coriacea are found. Turtles are netted and speared along entire Indian coast.
In South-east India, annual catch is estimated at 4,000-5,000 animals with C. mydas accounting for about 70% of harvest (Salm, 1981). E. imbricata is occasionally eaten, usually caught for its shell alone. D. coriacea is boiled for its oil which is used for protecting boats from marine borers.
In Gulf of Mannar, turtles are common near sea grassbeds, where shrimps trawler operate, but off the coast of Bengal growing number of mechanized fishing boats cause increase in incidental catch rates (Kar and Bhaskar, 1981). In Indian EEZ, present level of exploitation is 2.7 million tones, i.e., about 69 % of total exploitable potential. Species for increased production are Nemipterus sp.
Trichiurus sp., Saurida sp. Sphyraena sp., Tachysurus sp., Puerulus seqwlli. Bull’s eye, drift fish, scad, deep sea prawns are under exploited in Indian EEZ. Reassessing the marine biodiversity especially in well known sites like Gulf of Mannar has been emphasized. Inventorying marine biodiversity and integration of understanding of marine ecosystems with sustainable use of resources is urgently required.