The ‘Gangetic River Dolphin’ commonly known as – “RIVER DOLPHIN” is a biological curiosity. In North-East India, especially in the state of Assam, this endangered species locally called as ‘Hihu’, ‘Xihu’, ‘Seho’, ‘Huh’, in the big red river ‘Brahmaputra’ and its 13 tributaries. Scientifically known as Platanista Gangetica, species have some 5 species belonging to 3 genera. The species inhabit the waters of the Indian major rivers Ganga and Brahmaputra.
In India, their territory extends from the foot of the Himalayas to the tidal zone. Commonly known as Susu in Gangetic Valley and Hihu in the Brahmaputra Valley, the aquatic mammal, gangetic river dolphin is among the four fresh water dolphin species. Apart from India, it is also found in Bangladesh (in Meghna River and Karnaphuli River systems), Nepal and Bhutan.
The other three are the Baiji (that is, Lipotes Vexillifer) found in the Yangtze River in China, the Bhulan in Indus River of Pakistan and the Buto (that is, Inia Geoffrensis) in the Amazon River of Brazil in South America. In some areas, it is called as Suongsu. Indeed, out of 40 species of cetaceans, which live in the rivers, four species are found in Asia Continent and the two are found in South Asia.
“The history of the river dolphin is very interesting. This gangetic-river-dolphin developd about 20 million year ago. It was William Roxburg, who first described scientifically the species in 1801 and named it Dolphinus Gangetica. Later Rene Lesson then adopted a genus based on the dialect of Bengali, named Susuk and explained the species as Susu Platanista. But, Johann Wagle adapted Platanista as genus in 1930 and from that period, the scientific society knows the gangetic-dolphin as Platanista Gangetica, a close relative of Whales, Porpoises and Dolphins apart from Baiji, Bhulan and Buto”, claimed the experts.
The River Dolphins are specially dispersed in the river. Their concentrations are more in the confluences of the rivers, where the ‘water current’ is maximum and strong. In a word, the rising water level and water current greatly influence their movement and migration. They are also piscivorous and carnivorous.
Their body is fusiform. It can grow up to a maximum length of about 7.5 to 8.5 feet (2.3 metre to 2.6 metre). However, its length at birth is 67 centimetres to 70 centimetres. The smallest sexually mature female is around 200 centimetres and male 170 centimetres and age of maturity about 10 years, putting on about 90 kilograms to 100 kilograms in weight. In general, the females are larger than the males. The largest female was recorded at 252-centimetres long and the male 212-centimetres.
There are two species of River Dolphins in the river, one with a distinct dorsal fin and the other without it. Dorsally, a fleshy ridge forming a rudimentary fin is seen about mid length of the body excluding the beak. The pectoral flippers are more or less triangular and measure about one-sixth the length of the body. The flippers (fore arms) are broad and paddle like. The dorsal fin is short but the caudal fluke is well developed.
They have an elongated beak. The female has an upturned beak and the male has a straight beak. The number of teeth may vary from 27 to 32 on each side of each (upper and lower) jaw, there being a slightly higher count in the lower than in the upper jaw.
The River Dolphin is an aquatic mammal. They have no gills like fishes and therefore cannot breathe the oxygen dissolved in water. They breathe oxygen (O2) from the air with lungs. Without oxygen they cannot live. So, they have to come to the surface for breathing every 30 to 40 seconds and thus in one hour they have to surface about 100 times. But, when disturbed they remain underneath for more time. They are found to move both clockwise and anti-clockwise. Water temperature has no recognizable effect on their movement.
River Dolphins are found both in the rivers and the sea. The ‘Sea Dolphin’ has eyes; where as River Dolphin is blind. To compensate for their vision, they have developed their ‘Sound’ (which is called ‘Sonar System’ or ‘Sonar Sense’). They produce ultrasonic sound up to more than 200,000 hertz.
In natural populations, the male to female sex ratio of River Dolphins is 1:1. The calving season is observed to be from the month of March to May. Their gestation period is 8 to 9 months. But it has been noticed that one female in its life time gives birth to about 5 to 6 or rarely 7 to 8 young or calves and one or rarely two young are born between the months of April to July. The potential reproductive period is about 20 years.
The River Dolphin is not strictly a bottom feeder. It feeds both by day and night. The female River Dolphin feed their young ones with milk from the mammary glands located near its anus. Their food composes of small fishes, eel (locally called Kuchiya Machh) and loaches (locally called Botia Machh) besides a good amount of shrimps (that is, prawns). Their food requirement is about 10% (percent) of the body weight. About 40% (per cent) to 50% (per cent) of the body weight is ‘oil’ or ‘Fat’. The life expectancy is about 24 to 25 years and the life span of the species was considered to be about 35 years.
Besides the uses of its parts, the behaviour of River Dolphins helps to predict rain, flood and availability of fish. Presence of the bird ‘River tern’ indicates their population in the area. They are also seen in the tidal limits, but don’t enter the sea. Although the River Dolphin is found in small groups in certain parts of the rivers, it appears to be essentially non-gregarious.
In North-East India, the River Dolphin is found mainly in the river Brahmaputra and its tributaries, which are their original residential area. The fragmentation distribution system or the population status of the River Dolphin are the entire stretch or the river Brahmaputra traversing in North-East India; specially in Assam from Saikhowaghat (27° 51’44” North and 95° 39’12” East) in the upper most gradient down to South Salmara (25° 53’13” North and 90° 14′ 16″ East) at the lower reaches.
Specially three sectors with the respective ‘Trize Zones’ identified along the entire courses of the river were : Sector-I, Sector-II and Sector-III, Sector-I are Saikhowaghat to Silghat (trize zones; Saikhowaghat, Dibrugarh, Dikhowmukh, Nimatighat and Silghat), Sector-II are Silghat to Guwahati (trize zones : Tezpur, Singri, Kharupetia, Kharua and Guwahati) and lastly Sector-III are Guwahati to South-Salmara (trize zones : Garigaon, Kukurmara, Baghbar, Pancharatna, Kharmuja, Chunari, Jamadarhat, Fakirganj and South Salmara).
Of them, their population more localised at Dikhowmukh in Sector-I, Singri and Tezpur in Sector-II and Pancharatna, Baghbar and South-Salmara in Sector-III. Their total population in Brahmaputra river is around 1,300. The density of river dolphins has plummeted from 0.25 per kilometre of river length in 1991 to 0.09 per kilometre in 1996 in the Northeast Indian rivers, Ganga, Barak and Brhmaputra, which are their sanctuaries.
Around 1,326 specimens of River Dolphin has been estimated in the river Brahmaputra and its tributaries with sector wise distribution as 201 in Sector-I, 220 in Sector-II and 905 in Sector-III.
While another report claims, “It is also noted that the river Brahmaputra is divided into 6 segments in terms of dolphin habitat – from the Dhubri-Manas sector (under Indian Assam State’s Dhubri and Barpeta Districts) comprising India-Bangladesh International Border to Burhidihing-Sadyia sector (under Indian Assam State’s Dibrugarh and Tinsukia Districts) comprising Indian Interstate Border between Assam State and Arunachal Pradesh. Most of the time, the freshwater mammals are seen in Indian Assam State’s – (South Salmara) Dhubri district, (Pancharatna) Goalpara district, (Kulsi) Kamrup district and (Guijan) Tinsukia district”.
Moreover, this critically endangered species (xihu) is very dear to the people, which are also found in the other Indian States, Arunachal Pradesh, West Bengal (WB), Bihar and Uttar Pradesh (UP).
According to recent survey, there are 200 river dolphins in Brahmaputra and its tributaries like – Subansiri River (in Lakhimpur District of the India State, Assam) and Kulsi River in the aforesaid state. The dolphin population in all these sectors has recorded a steady decline – from 268 in 1993 to 198 in 2002, while in 2005, only the Dhubri-Manas stretch was surveyed, and just five dolphins were sighted against 17 in 2002.
In Assam, about 60 to 70 killings are made annually in the river Brahmaputra by the fishermen, who are locally known as – Bin community (that is, entangled in their fishing-nets and can’t come to the surface to breath and die a painful death). In North-East India, especially in Assam, River Dolphin killing occurs especially from Guwahati to South-Salmara (that is, Garigaon, Kukurmara, Baghbar, Pancharatna, Kharmuia, Chunari, Jamadarhat, Fakirganj and South-Salmara). Here, also juveniles are found to die in higher numbers. If the above same rate of killings continues, Dolphins in Brahmaputra River will be extinct within about another 20 to 25 years or so.
The River Dolphin was found in North-East India, especially in Assam in large numbers, a few years ago. Now, their number has come down considerably due to various human and non-human activities.
It is estimated that more than 70% to 75% of Dolphins are killed annually in the river Brahmaputra throughout its range from Saikhowaghat (under Tinsukia district of Upper Assam Sector) to South-Salmara-ghat (under Dhubri district of Lower Assam Sector) of North-East India.
The following reasons are the main threat to River Dolphin and the decline in their population :
(a) Heavy siltation, water removal, damming or dams or dikes or barrages, sluice-gates, fishing activities, poaching and vessel traffic (especially Engine Fit Country Boat-EFCB, locally known as shallow or Bhutbhuti).
(b) Environmental degradation seems to be a major cause.
(c) The drainage system of river Brahmaputra.
(d) They are killed largely for their blubber as oil, used as medicine for rheumatic pain or believed to be a cure for rheumatism, et cetera.
(e) To prepare the bait, intestines of fish, Catfishes, Clupisoma garuah (locally called Gharuah), Schielbids fishes get attracted by the smell of River Dolphin oil. Bihari and Bangladeshi fishermen mainly use this oil to catch fish. It is also noted that the River Dolphin oil was found in the open market for sale for Rs. 150 to Rs. 250 per litre.
(f) They are killed for their meat. The River Dolphin’s meat was found in open market for sale for Rs. 25 to Rs. 50 per kilogram. In Upper Assam, River Dolphin killing occurs especially Saikhowaghat, Dibrugarh, Dikhowmukh, Nimatighat and Silghat, primarily for its meat.
(g) The extraction of sand from riverbeds is a major threat to River Dolphin population growth.
(h) Industrial effluents, especially the discharge of fertilizers, petrochemicals – byproducts of tanneries and pulp and paper – mills, distilleries and thermal power plants.
(i) In the river Brahmaputra and it’s tributaries, the rampant fishing leads to the scarcity of small fishes (which are the River Dolphin’s basic food : Chela laubuca – known as Chela, Puntius sophore – known as Shwarputhi, Puntius ticto – known as Puthi, Colisa fasciata – known as Khailsha, Glassogobius giuris – known as Balia, Mastacembalus pancalus – known as Baim, Ompak sp – known as Pabda, Bagarius bagarius – known as Bagari et cetera). (j)
Biotic interference is the main threat of fresh water River Dolphin’s riverine habitat.
During a survey in the river Brahmaputra, there have also been an increase in different types of nets.
Monofilament gillnets are used by ‘migrant fisherman’ from Bangladesh (the then East Pakistan, that is, East-Bengal, known as Purba Banga or Purba Bangla). Some of the fishing centres in the river Brahmaputra are Dhubri, Fakirganj, Jogighopa, Goalpara, Dolgoma, Nagarberra, Kukurmara, Palasain, Guwahati, Biswanath, Behali, Dhansirimukh, Nimatighat, Disangmukk, Dikhowmukh, Dihingmukh, Dibrugarh, Saikhowaghat et cetera, where nearly 2,000 to 2,500 gillnets are operated.
(k) Food scarcity owing to excessive fishing and hydropower projects of various scales.
(l) Illegal catching, habitat shrinkage and excessive pollution.
River Dolphins are unique and they play an important role in the ‘River’s Ecosystem’. Today, the River Dolphin of the river (Ganges and) Brahmaputra are in great peril. They can be saved, if concrete efforts are made immediately. The chief cause of the survival of the species rests, finally in the hands of fishermen, who are unfortunately, poor and illiterate. They would have to be given an alternate means of livelihood.
Based on the letters and complains filed by the Dolphin Protection Committee (DPC) and Conservation of Nature Trust (CNT) the Government of Assam has issued an order to all District Administrators to take action against any killing of the River Dolphins or causing death to them. Presently, the River Dolphins are included in Schedule I of the Indian Wildlife Protection Act (IWPA), 1972.
According to this act, if anyone is found killing them or possessing any part of it can be imprisoned for 1 to 6 years and fined not less than Rs. 5,000 to Rs. 6,000. The observers also research or discuss the international laws like Convention on International Trade in Endangered Species (CITES), RAMSAR convention, World Heritage convention, Man and the Biosphere Programme (MAB) and the National laws of India, Pakistan, Bhutan, Nepal and Bangladesh. The Indian states laws of Uttar Pradesh (UP), Bihar, Arunachal Pradesh and Assam and Pakistan are also summarized.
Suggestions and recommendations are made to make the existing laws more efficient. This fresh water Dolphin has been classified as an endangered species by the International Union of Conservation of Nature (IUCN) in January, 1993 in their 19th Session of General Assembly. This species is recommended to be brought under “Rare” category, particularly in the Indian sub-continent. Although, it heads IUCN list of ‘vulnerable’ cetacean species, knowledgeable quarters in (Bangladesh) the Indian sub-continent already list it as an ‘endangered’ one. When present in large numbers, the river dolphin, which is at the apex of the aquatic food chain, indicates a healthy ecosystem.
The District Administrators of Dhubri, Goalpara and Jorhat of the Indian state, Assam issued a notification that the River Dolphins and other endangered animals should not be brought to the local fish market. The causes may be put forward for the preservation of River Dolphin :
(1) During monsoon, the River Dolphin descends to the tidal waters and is often taken in the different types of fishing nets. Such as : ‘Gillnets’ (locally called Fanshijal, Current net-Cast net), ‘Mosquito net’ (locally known as Masharijal), fine nylon ‘current net’ (locally called Kapdajal), ‘Neo-net’, ‘Dip net’ (locally called Dhekijal), ‘Stalk net’ (locally known as Banjal), ‘Moving-cast net’ (locally called Othaljal), ‘Drag-net’, large-encircling-seine nets (locally known as Berajal), harpoons et cetera should be banned.
(2) Banning the use of Dolphin oil as fish fait, burning lamps and for other purposes.
(3) Popularise ‘Shark Liver Oil’ or ‘Fish Oil’ as an alternative to the River Dolphin oil as bait for specially ‘Neria fish’ or scientifically known as Clupisoma garua, locally called Gharua fish. Because, a section of fishermen as the oil oozing out of their decomposed blubbers is used to attract a variety of catfishes, ‘Wallago attu’ (locally called Boal).
(4) To reduce the siltation and the soil erosion including various types of river pollution.
(5) Not to establish any industry on the bank of the river (especially Brahmaputra and its tributaries).
(6) Ban specialised impelling gear locally called Pusha.
(7) Medicinal uses like common cold or stomach disorders et cetera of River Dolphin’s oil should be discouraged and alternative medicines should be popularised.
(8) Not to extract sand from ‘River-Bed’ for it create hazards for their living.
(9) In North-East India, ‘Kulsi River’ and lower reaches of ‘Subansiri River’ of Assam declare as ‘River Dolphin Sanctuary’ and ‘Eco-tourism Centre’ as early as possible.
(10) Creation of mass awareness with more scientific studies among the ‘Fisherman’ community and from Schoolchildren to public about the endangered status of River Dolphin.
(11) To start fishery system in the riverines, this has inter-relation with River Dolphins and help to increase their numbers.
(12) To check the de-forestation and river erosion. Xihus surfacing intermittently from the deep waters to breathe before quickly disappearing again was a common sight earlier. However, over the years, their sightings have become rare.
Around 268 critically-endangered species, xihus are fighting a battle for survival in the rivers of the state, Assam and their number has come down drastically because of indiscriminate hunting and pollution. “Lack of public awareness is one of the reasons for fast disappearing Gangetic river dolphin in the rivers of eastern India”, said S. P. Bairagi of Dolphin Foundation organization.
Therefore, though, the World Wide Fund (WWF) for Nature India adopted the river dolphin as a species of special concern and initiated the Gangetic River Dolphin Conservation Programme in the year, 1997 and the Indian Assam State Government (IASG) on 05th June, 2008 declared the endangered species, Gangetic river dolphin as the ‘Assam State Aquatic Animal’, which was a longstanding demand of the various environmentalist groups across the world. On the other hand, Government of India declares the River Dolphin is a first ‘National Aquatic Animal of India’ on 5th October, 2009, during the first session/meeting of the National Ganga River Basin Authority (NGRBA), at New Delhi, the capital of India, which was proposed by the Indian Bihar State Chief minister, Nitish Kumar.
However, is the declaration to enough to save the rare fresh water species from the hand of its extinction? But, if the killing of the River Dolphin is not checked immediately it will be extinct within the next 10 years.
Caption of The Pix on River Dolphin: