Coastal Aquaculture and Mariculture

Unit 8- Deep sea fisheries

8.2.2. Conservation of endangered marine animals of India

Seacucumbers
Seacucumbers are a delicacy for the Chinese, the Japanese and Koreans. The processed seacucumbers commands good price in the international markets like Hong Kong, Singapore and Taiwan. In the world, there are about 1400 species. Of these, about 30 species are edible. In the seas around India about 200 species are known. Of these about 22 species were once abundant and they are now found to be overexploited. Commercially important species includes Holothuria scabra, H. nobilis, H. spinefera, Thelenota ananas, Actinopyge miliaris, A. echinites, A. mauritiana, Stichopus hermanni, S. cholronotus and Bohadschia marmorata.
Holothuria scabra and H. spinefera were indiscriminately collected at Gulf of Mannarwithout giving a chance for the animal to breed at least once during their life. To prevent the collection of smaller forms the Government of India imposed a ban in 1982 on the export of material, which is less than 75 mm in length. However, undersized materials were illegally sent out of the country as hand baggage. Hence, all the seacucumbers were brought under Schedule I list of the Wildlife Protection Act, 1972 and strictly banned their collection in 2001. It is suggested to have mass breeding and sea ranching programme to keep up the natural stock in the sea.
Turtles
Five species of marine turtle such as Green turtle Chelonia mydas, Loggerhead Caretta caretta, Olive Ridley Lepidochelys olivacea, Hawksbill Eretmochelys imbricata and Leatherback Dermochelys coriacea occur in Indian waters. Most of the marine turtle populations found in the Indian region are in decline. The principal reason for the decrease in numbers is deliberate human predation. Turtles are netted and speared along the entire Indian coast. In south- east India the annual catch was estimated at 4,000-5,000 animals, with C. mydas accounting for about 70% of the harvest. C. carella and L. olivacea are the most widely consumed species. E. imbricala is occasionally eaten but it has caused deaths and so is usually caught for its shell alone. D. coriacea is boiled for its oil which is used for caulking boats and as protection from marine borers. Incidental netting is widespread.
The coast of Orissa, in the eastern part of India on the Bay of Bengal, is the most important sea turtle nesting area in India and possibly the most important olive ridley nesting site in the world. In the Gulf of Mannar, turtles are still reasonably common near seagrass beds where shrimp trawlers operate, but off the coast of Bengal the growing number of mechanized fishing boats has had the effect of increasing incidental catch rates. In Gulf of Mannar, island based stake net operations have entailed heavy destruction by fisherfolk of the marine turtle eggs which are laid seasonally by the olive ridely on the seaward sandy beaches of almost all the islands. Drift netting in the zone of arrival of the turtles, traps the breeders coming in for nesting. Besides, this area also has been identified as an important feeding ground for green turtle and hawks-bill turtle. A fishing village on the Gulf Mannar coast, Periyathalai, known for turtle nesting from time immemorial, nowadays finds turtles very rarely.
Major threats include incidental and accidental catching, destructive fishing gears, exploiting the adult female when it comes to the beach for nesting, exploitation of eggs for human consumption, predation of eggs by dogs, ghost crabs and birds, predation of hatchlings by birds, sharks and fishes, beach erosion, habitat destruction and pollution. In addition to this, turtles are long-lived, slow to mature, low fecund and have low survival rate. All the five species of turtles occurring in Indian seas are protected as they are placed in Schedule I of the Wildlife Protection Act, 1972. India abides by the CITES which prohibits the trade in turtle products. To reduce the mortality due to incidental catch, two options namely closure of fishing during mass nesting period and attachment of Turtle Excluder Device (TED) to the trawl nets are suggested.
Marine Mammals
The world marine mammal diversity includes about 87 species of whales, .dolphins, porpoises and dugong. Marine mammals are among the most neglected groups in India as no concerted efforts have been made in the country even to collect basic information about them like species diversity, distribution and biological characteristics. Twenty six species of cetaceans and one species of Sirenia (Dugong) have been reported in the seas around India. Dugong, an endangered marine mammal, also known as Sea Cow, is only strictly marine mammal, which is hervivorous. It mainly feeds on sea-grass and other aquatic vegetation.
They are widely hunted for their flesh, oil and other products. Due to their large size, docile nature, low birth rate and long life span they become highly vulnerable to overexploitation. Thus many species have become rare or endangered. They frequent the coastal waters, for feeding or breeding, where they get entangled or entrapped in the fishing gears such as trawl net, gill net or purse seines that are operated for exploiting other resources. Although mammal fishery is banned, there have been clandestine attempts at their capture. The degradation and denudation of seagrass beds lead dugongs to seek similar pristine habitat elsewhere. Marine mammals migrate seasonally to tropical waters for breeding or to escape climatic extremes; during the course they get stranded in gently sloping beaches, murky water and tidal sites. Pollution caused by the discharge of industrial effluents particu1arly the hot water effluents and fly ash from the thermal power plants also affected the plankton diversity which in turn affected population of dolphin along the Gulf of Mannar coast.
Habitat degradation, predation of their calves by sharks, directed hunting, opportunistic netting and illegal capture are the major threats for the life of marine mammals. Hence, all the marine mammals including 11 species of whales, 14 species of dolphins, 1 species of Dugong dugon (Seacow) and 1 species of porpoise, Neophocaena phocaenoides (Little Indian Porpoise / Black Finless Porpoise) have been listed under the schedule I - Part I of the Wildlife Protection Act, 1972. International Whaling Commission has also declared the Indian Ocean as a sanctuary for the cetaceans. As they are protected under this act, there is no organized exploitation. However, there are clandestine catches of the most desired dugongs, which go either unnoticed or unreported. The suggestions to mitigate the anthropogenic threats are: (i) ban their catch, intentional or unintentional and the trade if any, (ii) replace the destructive gears with BED fitted gear, and acoustically opaque gill nets, (iii) establish marine parks and sanctuaries, (iv) curtail irrational fishing in vulnerable habitats and destruction of sea grass meadows and (v) creation of public awareness.
A notification without the promotion of conservation awareness programmes among the stakeholders and subsistence fishers could drive the trade underground and could divert the scarce resources towards enforcement. More emphasis should be laid on habitat improvement and pollution monitoring. Only effective management through strict regulation, periodic monitoring and sea ranching alone can save these vulnerable and endangered animals from further extinction.
Corals
There are about 793 living species of Scleractinian corals worldwide. A total of 199 coral species divided among 71 genera are hitherto recorded from India. Indian coral reefs have a wide range of resources which are of commercial value. Exploitation of corals, coral debris and coral sand is widespread on the Gulf of Mannar and Gulf of Kutch reefs, while seafans are exported for decorative purposes. The coral reefs of Palk Bay and Gulf of Mannar have been quarried for industrial purposes from early 60's from Mandapam to Tuticorin before the declaration of Marine Biosphere Reserve and National Park. About 10,000 tonnes of lime was manufactured annually by burning mainly species of Acropora in kilns in 1981. At Tuticorin alone one estimate was 80,000 t per year. Even though gorgonians are widely distributed all along the coast of India, they are abundantly seen on the South-east coast of India from Rameshwaram to Kanyakumari.
Deforestation, construction, coral mining and sand mining cause a lot of sedimentation and siltation on coral reefs. Recently, 2 islands viz. Vilanguchalli in Tuticorin group and Poovarasanpatti in Keelakarai group in Gulf of Mannar submerged under water due to coral mining. Sewage enriches the nutrients and thereby reduces the photosynthetic efficiency of corals. Destructive fishing practices like purse seining, bottom trawling, blast fishing and using fishing traps destroy corals. Ola valai and shore seines also cause damages to corals to certain extent. Mangroves and seagrass that normally act as filters for sediment are being rapidly destroyed. There has been an unprecedented increase in the number of coral bleaching events during the past two decades.
The Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, has classified many corals as threatened species. All the corals that include reef building corals (Scleractinans), black corals (Antipatharians), organ pipe corals, fire corals and seafans (Gorgonians) are protected under Wildlife Protection Act, 1972. India has 36 marine protected areas of which 20 comprise exclusively in intertidal/subtidal or mangroves, coral reefs, lagoons, estuaries, beaches etc., and the rest of the 13 include major parts of the marine ecosystem and some parts of terrestrial ecosystem. Awareness should be created among the coral reef resource users on the importance of conserving corals. Trawling in and around coral reefs should be prohibited. Existing laws should be enforced strictly.