The sea-cows or the dugongs are distributed in the Indo-Pacific region between 10ngitudes32°E and 1700W, latitudes 35° and 400N. There are five population namely, East Australian, North Australian, Andaman-Malay Peninsula, Thailand and South China, South Indian and Sri Lanka, East African, Red Sea and Persian Gulf

Lal Mohan, R S

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GOLDEN JUBILEE CELEBRATIONS22 The Sea Cow, Dugong Dugon Of India R.S. La) Mohan, Conservation of Nature Trust, 43~C, Water Tank Road, Nagercoil- 629001. The sea-cows or the dugongs are distributed in the Indo-Pacific region between 10ngitudes32°E and 1700W, latitudes 35° and 400N. There are five population namely, East Australian, North Australian, Andaman-Malay Peninsula, Thailand and South China, South Indian and Sri Lanka, East African, Red Sea and Persian Gulf. Dugong has a wide distribution in th~ tropical Indo - Pacific region. They are recorded from East Africa, Mafia Island, Kenya, Red Sea, Persian Gulf, Gulf of Mannar, Palk Bay, Sri Lanka, Andaman Island, Burmese Coast, Merqui Archepelago up to New Caledonia and Philippines Island. At present the dugongs are found in good numbers in the coast of Australia but becoming depl~ted in other places. The body of the dugongisspindle~ shaped and can be divided into head, trunk and tail. The head is small and characterised by the muzzle, a horse shoe shaped extension of the upper lip specialised to browse at the bottom of the sea. The surface of the muzzle has lllrge number of bristles. In the male a pair of insicors are found. The eyes aresmall. Nostrils are a pair of cresent shaped openings located dorsally. Ear openings are small without ear lobes. The dentition consists of incisors and molars, canines are not present. There are four pairs of incisors in the lower jaw in the yoWl! dugong but these are lost in the adult. When the teeth are shed, the sockets are filled with bony matter. Dugongs usually attain a maximum length of about 3 meters. Dugongs are well adapted for an aquatic life. The fore limbs .-e modified into flippers and the hind limps are absent. The pelvic girdle is absent and represented by two small bones. A strong caudal fluke is developed and help,the animal in propelling its body and to the swim. Two mammae, one on each. side are pre'sent near the arm pit of adult females. Nipples are about 25-30 mm in the adult females. In the male dugong, the urino-genital opening is situated away from the anus whereas in the female both openings are close. Bones are massive. It helps the animal to remain at the bottom of the sea. The brain of the dugong is small. Cerebrum has a few shallow sulci on temporal, parietal and frontal lobes. The corpus callosum is well developed. Pineal gland is absent in dugong. The kidneys are elongated. The ureters are dipelvic. In the males, testes are present posterior t~the kidneys. Penlsofth'e adult measures 20 - 25 cm in length. The ureters of dugong is bicornuated and the placenta non - deciduous. . Under the skin of the dugong is the blubber or fat layer constituted by fatty adipose tissue. It is useful to regulate the heat and protect the internal parts of the body from cold. The female dugong gives birth to one calf at a time. The foetus of the dugong may be about 90 cm. Dugong are monogamous. It matures at a length of about 23 m. Mimdapam Regional Centre of the Central Marine Fisheries Research Institute has the distinction of keeping the dugong in captivity for 10 years. It was observed to grow 47 cm adapted for an Ie modified into bsent. The pelvic ed by two small ;; developed and . body and to the I each ~jde are 'emales. Nipples t females. In the opening is whereas in the )se. Bones are ) remain at the f the dugong is allow sulci on )es. The corpus 'ineal gland is are elongated. lales, testes are ~nisof'th'e adult be ureters of the placenta lugong is the • fatty adipose eat and protect m cold. es birth to one 19ong maybe 10gamous. It ~entre of the Institute has Ig in captivity grow 47 em during this period. We do not have much information on its longivity. The longvity of the animal may.be about 40 years. Dugongs are herbivores. They feed on sea - grasses found in the coastal waters. The s!'a grasses Cymodocea ciliata, . C. isoetifolia, Enhaiuskoengi, Haiophila o valis, H. stipulacea, C. rotundata etc. form its main food. They are voracious feeders. 25 kgs of sea grass was taken from a dugong's stomach at a time. Dugongs browse at the bottom of the sea uprooting the rhizome of the sea grass. Sea grass · beds are found mainly · off Mandapam in the Palk Bay at about 5 kms. in length and 150 to 300 m in width. Near Hare Island and Manoli Island the seagrass beds are found as scattered patches. Luxuriant growth of Cymodocea serrulata is found from near Thondi to Athankarai. Near Sethu Karai also vast meadow of seagrass is found. Gulf of Ma~nar is characterised by a chain of twenty Islands and eighty one slightly elevated pearl banks locally known as 'paars'. Some of the islands are Vantivu, Velangli tivu, Musal tivu, Pallivasal tivu, Pulli tivu, Krusadi tivu etc. Dugongs occur in the sea grass beds found near the islands. As the seagrass beds are the main habitat of the dugong, any natural or man made degradation to the seagrass beds will be affecting the dugongs. Apart from the impact of bottom trawling, cyclones, tidal waves, flood and the effluents also can degrade the seagrass beds. Heavy damage was caused to the seagrass beds ofPalk Bay in 1954 cyclone. The tidal waves of 1958 1964 and 1.978 also have caused extensive damage to the seagrass beds of Gulf of Mannar and Palk'.Bay. It may be ' mentioned that during 1964, a tidal wave of 3-5m high struck the Rameswaram island washing away Dhanushkodi Island. Flood damage to these grass beds are well documented in India and Australian Coasts. 23 It was observed that many carcass of ~ugongs were washed ashore after the 1954 cyclone. The dugong population of Gulf of Kutch IS under great stress due to the development of petrochemical industr!es and disturbances to · the ecosystem caused by the effluents. Many large industries are located in Tuticorin and their effluents are letinto the Gulf of Mannar. 38 Dugongs in Saudi Arabia died after the Gulfwar. In India the gillnets are the major cause for the depletion of dugong population . In Tamilnadu there are about 1.18 million gillnets each measuring 2-3 . kms. Gulf of Mannar has about 86202 giIlnets and the Gulf of Kutch 7382. Between 1971-1975 as maily as 146 dugongs were caught in Palk Bay and Gulf of Mannar. The mortality was about 30 per annum. It is very . high rate of mortality. There might have been many unrecorded catches. 100-150 dugongs were caught annually in Gulf of Mannar part of Sri Lankan coasts. Gill nets, spears and dynamites have almost exterminated the dugong poulation. Being a sluggish animal it was an easy target for the fisherman. Further as medicinal properties were attributed to its meat, there is a good demand for it. The dugong population of Gulf of Mannar and-Palk Bay were under severe fishing pressure. There was a good population before 50 years. Meat of dugong was sold atKeelakarai regularly. They were using large gill nets namely 'Avuli Valai' having a mesh size of about , 15-18cm for fishing the dugongs. These nets measured about 1.5 to 2.0 km .in length an~ 5-7m in depth imd was made of cotton twisted twine or twisted acacia sticks 'of about 2.5mm thickness. It can be said that the dugong population of Gulf of MaQnar is on the verge of extinction. Fisherman also say that they do not observe the dugongs now. All these observations indicate the dugongs of Gulf of Mannar and Palk Bay are becoming rare. It is essential to conserve the dugongs of Palk Bay & Gulf of Manna.", The Indian wild life protection Act 1972 offers protection to this animal. But the law not properly implemented by the enforcing authorities. The dugongs were 24 killed as enough awareness was not created among the fisherman and the coastal population. Intense awareness programme is this only way to protect the animal thotlgh they are rare 

Sea Cow, Dugong Dugon of India

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Sea Cow, Dugong Dugon of India

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