Freshwater ecosystems are an integral part of the global water cycle, flow regulation, and effective functioning of associated ecosystems. Even though it comprises less than one per cent of the Earth’s surface, it carries diverse species and biodiversity. The freshwater ecosystem nurtures 9.5 per cent of faunal species. Among the fauna of the water ecosystem, the water Cetacean species holds a unique position because, according to Cetacean researchers, only four species of freshwater dolphins are found on the Earth. They are the Amazon river dolphins or Boto, the Baiji dolphins of the Yangtze River system, the Indus river dolphins or Bhulan dolphins, and the Gangetic dolphin.
The Ganga river dolphin, also known as Soso or “tiger of the Ganges,” is an important indicator aquatic animal found only in the Indian subcontinent. Due to its endemic nature and importance, Gangatic dolphins enjoy the status of the National aquatic animal of India.
Gangetic dolphins are one of the only four species of freshwater Cetacean in the world. The other three are the Amazon River dolphin or Boto, the Baiji dolphin of the Yangtze River system, the Indus River dolphin or the Bhulan dolphin. Even though this species has been included in Schedule I of the Indian Wildlife Protection Act, 1972, in Appendix II of the Convention of Migratory Species, in the appendix of CITES, the Ganga dolphin’s IUCN status is still endangered.
EARLIEST EVIDENCE
The Gangetic dolphin’s presence was recorded from the time of Emperor Ashoka. They were known as “Ganga-Puputaka” and enjoyed the privilege of protected animal status through a royal decree. This is mentioned in the Fifth Pillar Edict. Its presence is mentioned in “Baburnama” as Khokk Aabi or water hog. The same species is mythologically associated with the goddess Ganga or Ganga Matha and enjoys a sacred position.
The Gangetic dolphin was first scientifically identified and documented by William Roxburgh and Heinrich Julius Lebeck in 1801. Roxburgh named it Delphinus gangetica. Another person, Rene Lesson, gave another name, Susus Platanista. Earlier researchers thought the Ganagetic dolphin was a sub-species of the South Asian river dolphin. The scientific community agreed that the Indus and Ganga dolphins are not identical. In 1971, Pilleri and Gihr divided Ganga and Indus dolphins into two separate species. Their division was based on skull structure differences. So, Gangetic dolphins became Platanista gangetica gangetica, and the Indus dolphins became Platanista gangetica minor.
DIFFERENT NAMES OF GANGETIC DOLPHIN
The Ganga dolphin is commonly known as Susu in India, Shunshut in Bangladesh and Saunch or Sounch in Nepal. The other names are the following.
- French – Sousou, Plataniste du Gange
- Spanish – Delfin del Ganges
- Assamese – Hiho, Hihu
- Bengali – Hsuh, Shush, Shushuk
- Hindi – Bhagirath, Soons, Soos
HABITAT
Gangetic dolphins were present throughout the Ganga-Brahmaputra basin and Karnaphili-Sanga river basin. Their presence extended from tidal deltas to plains. But now their habitat is threatened, and their natural habitat that extended from 77 degrees east longitude to 89 degrees east has become fragile. Now, this species is restricted to the Ganga-Bhramaputra-Barak river system in India, Karnali, Saptakoshi and Narayani rivers in Nepal and Meghana in Bangladesh. In the past, only rocky barriers, high velocities, or shallow water were responsible for their distribution limitation, but now, various problems, including poaching and contamination, have resulted in habitat fragmentation.
In general, salinity defines the downstream limitation of the Ganga dolphin’s distribution, and they can live in brackish water, too, though they never enter the sea. They prefer a habitat with a temperature range of 5 degrees Celsius to 35 degrees Celsius and prefer habitats characterized by an eddy-counter current system caused by a point bar from sediments or sand bars and bridges where eddy-counter current systems are formed. Even though turbidity will increase in waters during the monsoon period, it is not an essential factor in determining the distribution of this species.
TAXONOMY
Kingdom – Animalia
Phylum – Chordata
Subphylum – Vertebrata
Class – Mammalia
Order – Artiodactyla
Sub-order – Odontocetia
Family – Platanistidae
Genus- Platanista
Species – gangetica
Sub-species – gangetica
PHYSICAL CHARACTERS OF GANGETIC DOLPHIN
These dolphins have long, pointed snouts, a general characteristic of all river dolphins. Both jaws contain sets of long, sharp teeth, which are visible even when their mouth is closed.
They have tiny eyes and are present above the mouth. Even though they lack crystalline eyes, which makes them effectively blind, they can detect the intensity and direction of light. Now you will have a question. How can they navigate without eyes? The answer is simple- Ecolocation.
They utilize echolocation for navigation and hunting. They have a sturdy, flexible body with a large flipper and a low triangular dorsal fin. They can weigh up to 150 kilograms and typically range from 70 to 90 kilograms. The dorsal fins are located two-thirds of the body length from the anterior end. The flippers are broad with a crenellated margin and with visible hand and arm bones.
Calves are chocolate brown in colour, and the colour of adult Ganga dolphins is greyish brown. In body size, females (2.4 to 2.67 m) are larger than males (2 to 2.12 m). Their body is covered with smooth and hairless skin.
Normally, they chase and hunt surface-dwelling fish species. For example, Rhinomugil corsula( Corsula mullet)is their preferred fish. Above all, they prefer active foraging behaviour in the morning and afternoon. They also prefer to drive prey into a particular area for community feeding.
The males mature earlier, and the females attain maturity at 10 to 12 years. Their gestation period is nine months (in some papers, it is 12 months). The mother takes care of the calf and remains together for about one year. At the time of birth, the newborn calves weigh about 4 to 5 kilograms and are about 70cm in size.
Since they spend most of their time in turbid water, we have limitations in monitoring their underwater life. Their short surface time also creates difficulty in the survey activities.
Another important feature in their life is migration. From October to April, the Gangetic dolphins move from the Ganges tributaries to the main channel.
WHAT ARE THEIR PRIMITIVE CHARACTERS?
Ganga dolphins bear some primitive characteristics that other freshwater dolphins lack. The following are the primitive characters
- Presence of caecum at the junction of the small and large intestines.
- Dorsal position of testis.
- Presence of subcutaneous muscle in between two layers of blubber.
THREATS
- Poaching — Oil and meat extracted from Ganga dolphins are utilized as liniment and aphrodisiacs. In some parts of India and Bangladesh, fishermen use dolphin oil to attract Catfish (Eutropiichythys and Clapisoma garica). Some tribes in remote reaches of the Brahmaputra basin hunt dolphins for food. In Bangladesh, pregnant women consume dolphin oil.
- Accidental Killings — Accidental killings occur due to collisions with vessels and entanglement in fishing gear, such as nylon gillnets.
- Construction — The development of hydropower and irrigation in the Ganga River prevents dolphin migration. This will lead to population segregation. Construction of the Faraka barrage destroyed suitable habitats above the barrage. The reason for this change was excessive siltation and growth of macrophytes. River Kosi carries the maximum slit load in the Ganga river system, which is the second highest in the world after the Huang River. The rate of sedimentation in Chhatra-Birpur upstream is 5.33, and the rate of sedimentation in Birpur-Baltara downstream is 2.83. The process of dredging also contributes to the destruction of dolphins’ habitat. The river water extraction for irrigation has lower water levels throughout species ranges, which also contributes to habitat loss.
- Pollution — Pollution affects their habitats. Large quantity of chemical pesticides reaches both the Ganga and the Brahmaputra rivers. Concentrations of HCh or hexa chloro cyclo hexane, hexa chloro benzene or Hcb and chlordane compounds, as well as perfluorinated compounds, affect the health of dolphins.
- Water quality — Water pollution caused by untreated sewage and industrial discharge destroys water quality. Oil exploration and refining activities increase the PAH contamination in rivers, especially the Ganga and Brahmaputra, resulting in the deaths of dolphins and other aquatic species.
IUCN STATUS OF GANGETIC DOLPHIN
According to the IUCN Red List, the Ganga river dolphin belongs to the endangered category.
GANGETIC DOLPHIN CONSERVATION STRATEGY
- Habitat protection and restoration with the help of local communities. With their help, dolphin monitoring units are formed. These monitoring units will closely monitor rivers, especially during the rainy season, to protect seasonally migrating dolphins. They also help authorities monitor poaching and poachers. If poachers are identified, strong legal actions are taken against poachers.
- Established the Vikramshila dolphin sanctuary to conserve and protect river dolphins.
- A program was started in Pakistan in 2000 to rescue stranded Indus river dolphins in irrigation canals or isolated pools. Authorities in India adopted a similar program to protect Gangetic dolphins.
- Now, the authorities promote dolphin-oriented tourism. It was first introduced as river tourism between Kolkata and Varanasi.
IUCN PRINCIPLE FOR DOLPHIN CONSERVATION
In 1997, an IUCN workshop at Rajendrapur, Bangladesh, on water development and fresh cetaceans elucidated and adopted the following principles for cetacean conservation.
- Gangetic dolphins require sufficient year-round freshwater flow to live. We should carry out activities to ensure it.
- Large fluctuations in the water flow should be avoided.
- Access to flood plans should be preserved to ensure natural spawning and rearing habitats for fish, which are the prey bases of the dolphin.
- Information on the river’s pre-development ecological conditions should be considered when future development decisions are made, and post-developmental empirical studies should be conducted.
- Impact study of multiple developments of environmental impacts.
NATIONAL DOLPHIN RESEARCH CENTRE
NDRC, or the National Dolphin Research Centre, is India’s first research centre for Gangetic dolphins. It was started on March 4, 2024, in Patna, Bihar.
Although the project received its first approval in 2013, it became a reality in 2024. The idea of NDRC was first proposed by renowned expert Mr. R.K Sinha.
It was established in Bihar because, in the past, Bihar accounted for fifty per cent of the world’s river dolphin population, and currently, the habitat is facing threats.
VIKRAMASHILA GANGETIC DOLPHIN SANCTUARY
In 1991, the Vikramasila Gangetic Dolphin Sanctuary was notified to protect threatened Gangetic dolphins. This sanctuary is located in the Bhagalpur District of Bihar state, India, and covers a 60-kilometre stretch of the Ganges River from Sultanganj to Kahalgaon in the Bhagalpur district.
NATIONAL AQUATIC ANIMAL OF INDIA
The first meeting of the National Ganga River Basin Authority, or NGRBA, under the Prime Minister of India, Dr Manmohan Singh, decided to confer the status of national aquatic animal on Gangetic Dolphins on October 5, 2009. Later, the Ministry of Environment, Forest and Climate Change notified Gangetic Dolphins as national aquatic animals on May 18, 2010.
According to a study published by Das et al., in 2022, the number of Gangtic dolphins is estimated to be 3320 with + or – 620 individuals.
