Save the Gangetic Dolphin for Healthy Ganges River
-Dr. Arvind Singh
A gangetic dolphin which is also known as Ganges River dolphin or Indian River dolphin is a very rare subspecies of mammal endemic to the Ganges and Brahmaputra Rivers and their tributaries in India, Bangladesh, and Nepal. It is probably extinct in Bhutan. The scientific name of the Gangetic dolphin is Platanista gangetica gangetica and is commonly known as ‘Susu’ in India. Being a mammal the Gangetic dolphin cannot breathe in the water, therefore it surfaces every 30-120 seconds. Because of the sound, it produces when breathing, the animal is popularly referred to as ‘Susu’. It is also called as ‘Fresh Water-Tiger’.
The Gangetic dolphin has the same position in a river ecosystem as a tiger in a forest ecosystem (both are at the apex of the food chain in their ecosystem). As the presence of a tiger in the forest is an indicator of a healthy forest ecosystem in the same way the presence of a Gangetic dolphin in the river is an indicator of a healthy river ecosystem.
Gangetic dolphins are the links between fresh water and people. They are among the oldest creatures in the world along with crocodiles, sharks, and some turtles. Mother of all rivers in India, the sacred Ganges is unable to sustain the only population of fresh water dolphins found in the country. Today the Gangetic dolphins are living a pathetic life in Indian rivers and are fighting a losing battle for their survival.
To save the Gangetic dolphin, the government of India has declared it as a National Aquatic Animal. This decision was taken in the first meeting of the National Ganga River Basin Authority (NGRBA) held in the Chairmanship of then Prime Minister Dr. Manmohan Singh on 5th October 2009 and it was formally notified on 5th May 2010.
Dolphins are considered as priority species. World Wide Fund for Nature (WWF) treats priority species as one of the most ecologically, economically and/or culturally important species on the planet. Therefore, their survival needs to be ensured in natural habitats.
Besides India, Bangladesh, and Nepal, presently fresh water dolphins are found in only two other places in the world, the Boto (Inia geoffrensis) of Amazon River in South America and the Bhulan (Platanista gangetica minor) of Indus River in Pakistan. However, the Yangtze River dolphin or Chinese River dolphin (Lipotes vexillifer) commonly known as Baiji of China has gone extinct in 2006. Baiji called “Goddess of Yangtze” is, in fact, the lost cousin of Ganges River dolphin (Susu).
Distribution Range of Gangetic Dolphin in India:
The long-bodied, sleek Ganges River dolphin in India is found in states of Uttar Pradesh, Uttarakhand, Bihar, Jharkhand, Madhya Pradesh, Rajasthan, West Bengal and Assam in Ganges and Brahmaputra rivers. Once River dolphins were of common occurrence in these states however today they have become rare due to drastic reduction in their numbers.
In the Ganges Valley it ranges into most of the major affluents, including some of their tributaries like the Sone, the Yamuna, the Chambal, the Gomti, the Ghaghra, the Gandak and the Kosi rivers.
In Brahmaputra valley Gangetic dolphin also ranges into many of the major tributaries like the Tista, the Gadadhar, the Champamat, the Manas, the Bhareli, the Dihang, the Dibang, the Lohit, the Disang, the Dikho, and the Kapili rivers. Gangetic dolphins live not only in the main channels but also during the flood season, in seasonal tributaries and the flooded lowlands. The distribution is restricted only by lack of water and by rocky barriers.
Physical Features:
A long thin snout, rounded belly, stocky body and large flippers are characteristics of the Ganges River dolphin. The teeth are visible in both the upper and lower jaws even when the mouth is closed. The teeth of young animals are almost an inch long, thin and curved; however, as animal progresses in age the teeth undergo considerable changes and mature adults become square, bony, flat disks. The snout thickens towards its end.
The body is greyish brown in color. The calves and young ones are dark in color but as the animal growth in size, the colour lightens. The species has only a smaller triangular lump in the place of a dorsal fin. The flippers and tail are thin and large in relation to body size. Mature adult males are smaller than females with 2.12 and 2.67 m, respectively. Sexual dimorphism is expressed after females reach about 1.5 m. The female rostrum continues to grow after the male rostrum stops growing, finally reaching approximately 20 cm longer. The body weight is approximately 90 kg.
The eyes are extremely small, resembling pinhole openings slightly above the mouth. One of the characteristics of the Gangetic dolphin is that they are blind due to absence of crystalline eye lens. Hence the species is also referred as “Blind dolphin”. The river dolphin vision has probably degenerated because of the poor visibility of the waters in Ganges River. The dolphin still uses its eye to locate itself. It depends on echolocation to find the path. For this unique feature it is invaluable to science. The Ganges River dolphin has a slit similar to a blowhole on the top of the head, which acts as nostril.
Habitat and Ecology:
Gangetic dolphin is found exclusively in fresh water habitat which extends in one of the most densely populated region of the world. In India and Bangladesh individuals live in rivers that flow slowly through the plains while in Nepal, it inhabits clear water and rapids. The dolphins number are greater at sites where rivers join or just downstream of shallow stretches, in areas where the current is relatively weak, off the mouth of irrigation canals, and near villages and ferry routes.
The Gangetic dolphin is favored by deep pools, eddy counter-currents located downstream of the convergence of rivers and of sharp meanders and upstream and downstream of mid-channel islands. Dolphins concentrate in locations of high prey availability and reduced flow.
The Gangetic dolphin is favored by deep pools, eddy counter-currents located downstream of the convergence of rivers and of sharp meanders and upstream and downstream of mid-channel islands. Dolphins concentrate in locations of high prey availability and reduced flow.
Gangetic dolphin shares its habitat with crocodiles, water turtles, and wetland birds, many of which are fish eaters and are potential competitors with dolphins.
The dolphin has the peculiarity of swimming on one side so that its flipper trails the muddy bottom. Therefore, it is also called as ‘Side-swimming dolphin’. This behavior is understood to help it to find food.
The Gangetic dolphins feed on a variety of shrimp and fishes including carp and catfish and possibly turtles and birds. They normally chase surface dweller fishes and grovel mud dweller fishes in shallow water with help of their long snout. Gangetic dolphins cannot chew and usually swallow their prey. They catch their prey by emitting an ultrasonic sound to gauge distance, mass, etc.
Gangetic dolphins do much of their feeding at or near the bottom, echolocating and swimming on one side. The long beak is possibly an adaptation for extracting prey from crevasses or buried in soft sediment.
One calf is usually born once every 2 to 3 years and the gestation lasts from 9 to11 months. There is no specific birth period, although females usually give birth from October to March, with a peak in December and January at the onset of the dry season. After around one year, juveniles are weaned and they reach sexual maturity at about ten years of age.
There has been marked seasonal change in Gangetic dolphin distribution and density over much of its range because due to fluctuations in water levels. During the dry season from October to April, many dolphins leave the tributaries of the Ganges-Brahmaputra systems and congregate in the main channels, only to return to the tributaries the following rainy season. During the process, they often become isolated in pools and river branches during the dry season.
Threats to Survival:
The main threats to the survival of Gangetic dolphins include poaching, habitat degradation, river water pollution, accidental killing, over-exploitation of prey and river fragmentation. According to WWF study, 95% of dolphin deaths are directly attributed to man related causes. In 1982 dolphin population in Indian rivers ranged from 4,000 to 5,000 individuals. However, today their population has shrunk to serious extent in its entire distribution range in Ganges and Brahmaputra River system (around 6,000 km) ranging between 1,200 to 1,800 individuals. Thus Gangetic dolphin is a highly threatened mammalian fauna standing on the brink of extinction.
Poaching: Dolphin poaching is rampant in Ganges River. Gangetic dolphins are hunted for blubber. The oil extracted from blubber is used as a fish attractant and as medicine in curing joint pains and also as an aphrodisiac. This oil fishery is associated with the mortality of hundreds of dolphins every year. The poaching of Gangetic dolphin occurs in the middle Ganges near Patna and in the upper reaches of the Brahmaputra River in Assam. In Assam Gangetic dolphins are killed for their meat which is sold in the market and is also considered as aphrodisiac. Habitat degradation
There has been a substantial decline in the extent of the occurrence of Gangetic dolphin, as well as in the quality of their habitat, especially in the Ganges River Basin. This decline has been owing to the construction of an extensive network of barrages since the late 1950s. The species is severely fragmented and additional barrages continue to be built (for instance, Kanpur barrage on the Ganges mainstream).
The building of more than 50 dams and irrigation-related projects has adversely affected the habitat of Ganges River dolphins. These projects resulted in major changes in the flow, sediment load and water quality of rivers unfavorable for the survival of Gangetic dolphins. The building of dams along many rivers has divided dolphin populations into small segregated sub-populations preventing migrations and reducing food availability. The isolated dolphin populations have become more vulnerable to fishermen.
Besides fragmenting dolphin populations, dams and barrages prevent dolphins from swimming up and down rivers, degrade downstream habitat and create reservoirs with high sedimentation and altered assemblages of fish and invertebrate species. Just above the Farakka-Barrage luxuriant growth of macrophytes and excessive siltation has adversely affected the habitat of river dolphins.
The insufficient release of water downstream of the barrage has eliminated dry season habitat for more than 300 km or until the Ganges-Brahmaputra confluence and resulted in salt water intruding on additional 160 km into the Sunderban Delta, further decreasing the habitat for this obligate fresh water subspecies.
The insufficient release of water downstream of the barrage has eliminated dry season habitat for more than 300 km or until the Ganges-Brahmaputra confluence and resulted in salt water intruding on additional 160 km into the Sunderban Delta, further decreasing the habitat for this obligate fresh water subspecies.
Irrigation canals in the Ganges River may have brought prosperity to the river basin, but are a bane for the unfortunate dolphins in Ganges River. As water is drawn away from barrages for irrigation, large tracts of the river have become too shallow for the dolphins to survive.
Siltation from deforestation has also degraded the dolphin’s habitat. Habitat alterations have resulted in the genetic isolation of the dolphin population.
Other sources of habitat degradation include dredging and the removal of stones and sand. These activities threaten the ecological integrity of the riverine environments, particularly in small tributaries where suitable habitat is more confined and therefore more vulnerable to local sources of degradation. Suitable habitat is also threatened by water extraction from surface pumps and tube wells, especially from the Ganges where the mean dry season water depth has been dramatically reduced in recent years. The long-term implication of the reduction of dry-season flows in the Ganges River is harmful to the survival of Gangetic dolphins.
Pollution: River water pollution has adversely affected the proliferation of Gangetic dolphins. Poisoning of the river water from industrial and municipal effluents and agricultural chemicals has substantially contributed to the population decline of River dolphin.
Gangetic dolphins are vulnerable to industrial pollution because their habitat in counter-current pools downstream of confluences and sharp meanders often places them in close proximity to point sources in major urban areas. Moreover, because of upstream water extraction, the capacity of rivers to dilute pollutants has been drastically reduced in many areas.
Cultivation on the fertile alluvial banks of the Ganges River use organochlorine and organophosphate pesticides which drains into river and poisons dolphins. Compound organochlorine found in the blubbers of Gangetic dolphins is a cause of concern about its potential effects on the subspecies.
According to Conservation of Marine Species “about 1.15 million metric tonnes of chemical fertilizers and 2, 600 tonnes of pesticides are dumped annually in the river system” of India. For instance, the heavy metal-laden effluents from tanneries in Kanpur make the river very contaminated. Kanpur city is merely 165 km from the National Chambal Sanctuary in Etawah District of Uttar Pradesh where a significantly large number of Gangetic dolphins have been recorded.
The bioaccumulation of trace elements like lead, arsenic, and mercury are playing their part in gradually reducing the vitality and health of the dolphins.
Accidental killing: Accidental killing of Gangetic dolphins is a serious problem throughout most of their distribution range in India. The primary cause is entanglement in fishing gear, most often in nylon gillnets. The increased use of monofilament nylon fish gillnets by fishermen has killed dolphins over years than the poaching. Gillnets are usually made of very fine nylon thread and dolphins usually fail to echolocate them.
Gangetic dolphins are vulnerable to entanglement in gillnets because their preferred habitat is in the location where fishing is done on a large scale. The rate of accidental killing is expected to increase as the demand for fish and fishing employment is increasing.
Gangetic dolphins are vulnerable to entanglement in gillnets because their preferred habitat is in the location where fishing is done on a large scale. The rate of accidental killing is expected to increase as the demand for fish and fishing employment is increasing.
Accidental killing through gillnet and poaching of dolphin for oil are most dangerous threats to the survival of Ganges River dolphins. Accidental killing was the main factor behind extinction of Chinese River dolphin (Baiji) in China.
Over-exploitation of prey: Over-exploitation of prey, mainly owing to the widespread use of non-selective fishing gear during fish breeding migrations and early juvenile growth is also a threat to the survival of Gangetic dolphin. Over-exploitation of prey generally causes a scarcity of food for River dolphins.
River fragmentation: River fragmentation is another threat to the survival of dolphins. It refers to a decrease in river depth and the appearance of sand bars dividing the river course into smaller segments. The resident population of Gangetic dolphins in the Chambal River is threatened due to river fragmentation.
Conservation:
In the year1994, the International Union of the Conservation of Nature and Natural Resources (IUCN) has declared a Gangetic dolphin as ‘Vulnerable’, however, two years later in 1996, it was up listed as ‘Endangered’ in the Red List of Threatened Species. Gangetic dolphins have been listed as Flagship species by WWF. Moreover, this mammalian species is listed on Appendix I of Convention on International Trade in Endangered Species (CITES) and Schedule I of the Indian Wild Life Protection Act, 1972. Hence, poaching of the species and both domestic and internal trade in the species and its parts and derivatives are completely prohibited.
The Gangetic dolphin is listed on Appendix I and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I as this species has been categorized as being in danger of extinction throughout all or a significant proportion of its range and CMS Parties strive towards strictly protecting the animal, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them.
Gangetic dolphin is listed on Appendix II as it has an unfavorable conservation status or would benefit significantly from international cooperation organized by tailored agreements.
Vikramshila Gangetic Dolphin Sanctuary located in Bhagalpur district of Bihar is the only protected area established in Asia for protection and conservation of Gangetic dolphins. The Sanctuary is 50 km stretch of Ganges River from Sultanganj to Khalgaon, designated in 1991. The Sanctuary also supports a rich diversity of other wildlife. Unfortunately the Sanctuary has no formal conservation plan and many local people are unaware of its protected status and regulations.
Hence Gangetic dolphins face several threats in the Sanctuary which include competition with a human for food and water resources, physical alteration, habitat degradation, deliberate hunting for dolphin products such as meat and oil, pollutant load of the river and destructive fishing activities which results in high mortality from accidental killing and reduced availability of prey.
Besides supporting a relatively high density of dolphins, the Sanctuary also supports a rich diversity of other wildlife, many of which are threatened with extinction. These species include the Gharial, Indian smooth-coated otter, several species of hard-and soft-shell turtles, and a variety of migratory and resident migrating birds.
Hence Gangetic dolphins face several threats in the Sanctuary which include competition with a human for food and water resources, physical alteration, habitat degradation, deliberate hunting for dolphin products such as meat and oil, pollutant load of the river and destructive fishing activities which results in high mortality from accidental killing and reduced availability of prey.
Besides supporting a relatively high density of dolphins, the Sanctuary also supports a rich diversity of other wildlife, many of which are threatened with extinction. These species include the Gharial, Indian smooth-coated otter, several species of hard-and soft-shell turtles, and a variety of migratory and resident migrating birds.
The following actions are needed for the conservation of Gangetic dolphin in India:
1. To regularly monitor the population of Gangetic dolphin in Indian rivers.
2. To create protected areas for the Gangetic dolphin.
3. To restore the degraded habitats of Gangetic dolphin.
4. To create awareness about Gangetic dolphin among communities living along the bank of Ganges River and involve people as key partners in the conservation of Gangetic dolphin.
5. To promote Gangetic dolphin as a ‘flagship species’ of healthy rivers.
6. To conduct focused conservation efforts in those areas where there is an abundance of Gangetic dolphins.
7. To promote oil made from fish scraps as an alternative to dolphin oil for attracting fish as bait.
8. To strictly enforce the Indian Wildlife (Protection) Act and CITES.
2. To create protected areas for the Gangetic dolphin.
3. To restore the degraded habitats of Gangetic dolphin.
4. To create awareness about Gangetic dolphin among communities living along the bank of Ganges River and involve people as key partners in the conservation of Gangetic dolphin.
5. To promote Gangetic dolphin as a ‘flagship species’ of healthy rivers.
6. To conduct focused conservation efforts in those areas where there is an abundance of Gangetic dolphins.
7. To promote oil made from fish scraps as an alternative to dolphin oil for attracting fish as bait.
8. To strictly enforce the Indian Wildlife (Protection) Act and CITES.
Conclusion:
It can be concluded that Gangetic dolphin which is an indicator of river health is threatened mainly due to poaching, habitat degradation, river water pollution, accidental killing, over-exploitation of prey and river fragmentation. Therefore, it is the need of the hour to protect and conserve the Gangetic dolphin for the maintenance of the health of Ganges River.
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Dr. Arvind Singh is M. Sc. and Ph. D. in Botany with area of specialization in Ecology. He is an dedicated Researcher having more than four dozen of published Research Papers in the Journals of National and International repute. His main area of Research is Restoration of Mined Lands. However, he has also conducted Research on the Vascular Flora of Banaras Hindu University Main Campus, India.keywords: ganga dolphin, gangetic river dolphin, vikramshila gangetic dolphin sanctuary, gangetic dolphin information, vikramshila dolphin sanctuary, gangetic dolphin iucn, ganges river dolphin habitat, gangetic dolphin endangered, gangetic dolphin scientific name, gangetic dolphin is a type of which species, gangetic dolphin in india