Alaka Hujuri
Assistant Professor, Department of Economics
Bimala Prashad Chaliha College, Nagarbera, Kamrup, Assam, India

Biodiversity is threatened by different way by disruptions to the natural ecosystem. Loss of biodiversity has limited the resources needed by an organism and also it has affected in a way of chain model by altering its behavior how that organism interacts with other organisms. Ganges River dolphins occur in the Ganges-Brahmaputra River system primarily in India and Bangladesh. River Dolphins are declared as Endangered by the International Union for Conservation of Nature (IUCN) due to probable population decline of at least 50% over the last 50 years and expecting future population declines. To save dolphins from extinction, the Union government has declared them as the national aquatic animal. Since the river Dolphin is at the apex of the aquatic food chain, its presence in adequate numbers symbolizes greater bio-diversity in the river system. So, it becomes an alarming factor to protect this species to protect the biodiversity. This study aims to analyse the distributional trend of river dolphin in Brahmaputra River and try to find out the proper management options for river dolphins in the Brahmaputra river system.

Key words: Brahmaputra River, Gangetic dolphin, Conservation, Distributional status, Kulsi River, Subansiri River

1. Introduction

The Ganges River dolphin, (Platanista gangetica gangetica), is one of the mostcharismatic mega-fauna of the Indian subcontinent. It is among the four freshwaterdolphins found in the world. The others are the 'bhulan' ( Platanista gangeticaminor) in the Indus River in Pakistan, the 'baiji' (Lipotes vexillifer) in the Yangtze River in China, and the 'boto'  (Iniageoffrensis) in the Amazon River. The 'baiji' was reported to be functionally extinct in 2006 (Sinha et al., 2010). The Ganges river dolphin is primarily found in the Ganges and Brahmaputra Rivers and their tributaries in Bangladesh, India and Nepal. The Ganges subspecies (P. g. gangetica) can be found along the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu River systems of Bangladesh and India, although its range formerly extended to Nepal. The species has been facing severe threats as its global population decline, for which IUCN (International Union for Conservation of Nature) categorized the species as Endangered in 1996. It has been assessed that at present the species has not more than 2,500 individuals throughout its distributional ranges. The Government of India declared the animal as “National Aquatic Animal” on 5th October 2009 and a formal notification was issued by the Ministry of Environment and Forests on 10th May 2010 (Sinha, 2011). Just as the Tiger represents the health of the forest and the Snow Leopard represents the health of the mountainous regions, the presence of the Dolphin in a river system signals its good health and biodiversity.It is an excellent indicator of reverie ecosystem health. So, the declining trend of dolphin is an alarming fact for the environmentalists because it also signifies the deterioration of aquatic biodiversity. The IUCN changed its status from ‘Vulnerable’ to ‘Endangered’ in 1996 as its population was declining in its entire distribution range (Sinha, 2011).

In 19th century, these Dolphins are abundance in entire distributional range, though no actual data for that time is available. Dolphins played in rivers were a common picture for the fishermen and people related to reverie ecosystem.The river dolphin occupies the apex of the food chain of the river and plays a vital role in maintaining the essential balance of its ecosystem. Being a flagship species representing an ecosystem, its status has become a matter of serious concern to its existence over the past few decades. Therefore, there is an urgent need to identify the major threats of this endangered species and proper execution of the management or conservation options by improving the status of its habitat.

2. Objectives

  • To find the distributional pattern of river Dolphin along the Brahmaputra and its tributaries.
  • To identify threats to the habitats of Dolphins and suggest conservative measures for their protection.

3. Methodology

The study is based on secondary data. Secondary data required for the study are collected from books, journals, periodicals and reports of the Government and other agencies. Distributional status of dolphin in Brahmaputra River and its two tributaries are taken into consideration for the study.

The Brahmaputra flows through Tibet, India (Arunachal Pradesh & Assam) and Bangladesh and is one of the longest rivers in the world. After entering India the river flows as the Siang or Dihang River about 52 km from Pasighat in the foothills of the Himalayas before its confluence with two other major rivers, namely the Dibang and the Lohit. From this large confluence, the river is known as the Brahmaputra.

Kulsi River is in the Kamrup district of Western Assam. The river originates from Meghalaya where it is known as the Khri River. After traveling about 12 km from its origin, the river enters Kamrup district in Assam at Umkiam and is known as the Kulsi. The river finally discharges into the Brahmaputra at Nagarbera. The river is about 76 km in length from Kulsi town to the Brahmaputra confluence.

Subansiri is the largest tributary (443 km) of the Brahmaputra River and it originates from Purum peak in Tibet, where it is known as Lokong Su. From its origin the river crosses about 143 km through Tibet and then enters into Arunachal Pradesh of India. The River crosses about 191 km through Arunachal Pradesh and finally enters Assam near Garukamukh of Lakhimpur district. It crosses 37 No. National Highway at Sawoldhuwaghat, which is about 10 km downstream of Garukamukh. The river finally discharges into the Brahmaputra at Jamugurighat which is about 99 km downstream from Sawoldhuwahghat (Wakid, 2009).

4. Results and Discussion

4.1 Distributional Pattern

The first ever population survey about dolphin habitats was conducted in 1993 (Mohan et al. 1997).  Mohan et al. (1997) surveyed the main stream of Brahmaputra River from 15th February to 18th March, 1993 and they observed 266 dolphins in the entire river, from Sadiya (Assam-Arunachal border) to South Salmara (India-Bangladesh border), although they estimated the population at around 400 ((Wakid and Braulik, 2009) .They counted maximum number of dolphins in the river stretch from Tezpur to Guwahati (Behera et. al., 2012).

After 12 years an extensive population status survey was done by Wakid (2005) in the 1031 km dolphin habitats in Brahmaputra river system in 2004-2005. During that survey it was recorded altogether 250 dolphins in 101 habitats.In Subansiri River 26 dolphins (six calves, five sub-adults and 15 adults) were recorded, spreading in 11 locations of the river with an encounter rate of one dolphin per 4.15 km.  Altogether 15 Dolphins (two calves, five sub-adults and eight adults) were recorded spreading in 4 locations in Kulsi River with an encounter rate of one dolphin per 2.0 km and in Brahmaputra River, altogether 197 dolphins (27 calves, 32 sub-adults and 138 adults) were recorded from 82 locations of the river with an encounter rate of one dolphin per 4.2 km. The survey recorded maximum dolphins in the stretch from Dhansirimukh to Silghat. Majority (74%) of the dolphins within this stretch are within Kaziranga National Park. 

After four years, another survey (Wakid and Braulik, 2009) indicated a different distributional pattern of the species in entire Brahmaputra range. The sum of the best estimates of group size for the entire survey indicated 264 dolphins in the entire Brahmaputra River system, with 212 individuals in the Brahmaputra mainstream and an encounter rate of 0.24 Dolphin/km. Altogether 71 km of the Kulsi River was surveyed from Ghoramara to Nagarbera, where the river discharges into the Brahmaputra River. A best estimate of 29 dolphins was recorded. Again, 94 km stretch of Subansiri River was surveyed, from Katoi Sapori to Jamuguri, where the river discharges into the Brahmaputra mainstream. A best estimate of 23 dolphins was recorded with an encounter rate of 0.24 Dolphin/km.

The population status of dolphins in Brahmaputra River and its tributaries are given in Table 1

 Table 1: Population status of Dolphins in Brahmaputra River and its tributaries

Name of the river
Dolphin  number
400 (1993)
Mohan et. al. (1997)
197 (2004-05)
Wakid ( 2005)
Wakid and Braulik ( 2009)

25 (1993)
Mohan et. al. (1997)
Wakid and Braulik (2009)

Wakid and Braulik (2009)

From the comparative analysis of records of 2005 and 2009 in the Brahmaputra mainstream, for the slight increase in the number of dolphins may be in Dhansirimukh to Tezpur is likely to be the strict protection of the Brahmaputra by the Kaziranga National Park (Wakid and Braulik, 2009).

In the Subansiri River, Wakid in 2005 recorded a best estimate of 26 Dolphins, whereas it recorded 23 dolphins in 2008. Mohan et al. (1997) recorded altogether 25 dolphins in the Subansiri River in 1993 and from Dikrangmukh to Subansirimukh (22 km) a higher encounter rate of 1.13 Dolphins/km. However, due to the difference in survey methodology, these results are not comparable. The declining trend may be that large numbers of dolphins in this river were killed during the 1950 great earthquake and that the local ‘Missing’ tribe people killed the dolphins for meat, which often were brought to the Jengraimukh fish market (Wakid and Braulik, 2009).

In the Kulsi River, estimated number of Dolphin increases from 27 to 29 in the period from 2005 -2008. The highest Dolphin abundance was recorded in the first sector of the river from Ghoramara to Jarabari however all these Dolphins were concentrated in an 8 km long river stretch between Borpit to Jiakur. Mohan et al. (1998) reported sand mining as the greatest threat to the dolphins of the Kulsi River. He reported that the population was declining from 1992 to 1993 at a rate of 14-29%. However, in the surveys in 2005 and 2008 there was no evidence of a population decline. One reason that the population does not appear to be declining may be due to an increase of awareness by the local people. The local communities of Kukurmara and other fringe villages of Kulsi River strongly believe that killing of dolphins will be harmful to their families. This was reported by Mohan et al. (1997 & 1998) and this traditional belief continues. However, the dolphin hotspot in the Kulsi River is only approximately 40 kms from Guwahati, the capital city of Assam. Due to wide publicity by the local media in recent years, the Kukurmara area of the Kulsi River is now a tourist attraction for dolphin observation. A good number of tourists visit this area every year, which has directly inspired the conservation awareness among local people. Another factor may be that the major livelihood of the villagers in this area is sand mining, not fisheries as is the case in all other Dolphin habitats of Assam. The lower fishing effort in the Kulsi River may mean that prey is more abundant in this river than elsewhere. The river stretch from Borpit to Jiakur is surrounded by wetlands, (Koloni, and Sol beel on the northern side and Dora beel on the southern side) which are spawning sites for riverine fish which may increase the food supply for Dolphins in this stretch of the river.  Although the high rate of sand mining is one of the major disturbing factors to the dolphins of this river, it has had the effect of maintaining or possibly increasing the depth of this part of the river which may have a positive effect on the Dolphins. (Wakid and Braulik, 2009).

4.2 Major Threats
Accidental killing of dolphin through gill net entanglement, poaching, population fragmentation through water development projects, water pollution and over-exploitation of fish fauna, are the major factors threatening the Gangetic Dolphin subspecies (Sinha etal., 2000). Water development projects and water pollution are not the major threatening factors for the dolphins of Brahmaputra Valley at present and accidental killing through fisheries by-catch is thought to be the major threat for the dolphins in the Brahmaputra River. Out of the 16 recorded in 2008, 12 were the victim of by-catch mortality and rest were the victim of poaching.

 Dolphins are killed for meat and oil. ‘Missing’ tribes of Eastern Assam kill dolphins mainly for meat, whereas in Western Assam, they are killed for oil.(Mohan et al., 1997). Most of the riverine villagers in remote areas believe that dolphin oil has medicinal value and they use it to treat different rheumatic diseases (Wakid, 2005). Dolphin poaching for medicinal oil and for the oil bait fishery is one of the major causes of Dolphin mortality in Assam. Therefore extensive community-based conservation initiatives or awareness programmes can reduce the mortality rate of this species.
Industries discharging pollutants to water of Brahmaputra River pollutes the Dolphin habitats. Again, deforestation in the riparian zones and in highlands of Assam and Arunachal Pradesh has been creating siltation in the river bed, resulting into the lowering of water depth. Since Dolphins prefer deeper water, therefore, low water depth through siltation has resulted into habitat loss.

5. Policy Implications

The communities residing near important Dolphin habitats must be identified.By organizing informal meeting with the community and fishermen leaders and conveying its conservational needs, the habitat loss of this species can stop to some extent. That is, informal awareness campaign may beone of the fruitful conservative measures to protect this species.

During the time of high water season (monsoon season) dolphins usually make upstream migration through the small channels and tributaries of Brahmaputra River and coming down during the decreasing of the water level. During that time sometimes the Dolphins get entangled for their attempts to passing through the nets.  Raising awareness among the fishermen communities and villagers about the legal status of the species may be the remedy for its protection. Again, legal procedures against any reported killing of the species is necessary for its protection.

Determination of the level of pollution of the dolphin habitats in Brahmaputra River through intensive research by the research institutes of Assam is at most necessity. And level of deforestation in the riparian zones should be minimized by raising awareness and increasing the management strictness.

There are altogether 168 proposed dams in north east India, which will directly affect the dolphins in Brahmaputra river system. Therefore, the management authorities have to find out alternate approach to protect the species.

Extensive use of various types of gill nets in the entire Brahmaputra Valley over last 15 years resulting into the sharp declining of the fish fauna from this region, which has been directly affecting the Dolphin population in this region through shortage of food.  Therefore, strictness of the legal actions against over-fishing and using of banned gears by the state fishery department, Govt. of Assam and providing alternative livelihood to the fishermen communities during the fishing banned seasons are the suggestive measures (Wakid, 2007).

6. Conclusion

Last but not least, identification of the protected area for the Ganges river Dolphin and developing this area as potential tourist point may be one of the best measures to protect and nurture this endangered species. For example, Wakid identified that Kuruwa-Suwalkushi Stretch of Brahmaputra River as protected area for high dolphin abundance and potential for future dolphin tourism in 2009 since Guwahati City is situated on the bank of this stretch of the Brahmaputra. Again, Borpit-Jiakur river stretch of Kulsi River is also identified as protected area for high dolphin abundance and for having prospect for Dolphineco-tourism as it has good accessibility fromGuwahati city.By protecting dolphin community, it may be protection of rich biodiversity along with generation of employment through the huge scope of eco tourism.

  •  A. Wakid (2005). Conservation of Gangetic dolphin in Brahmaputra river system, India.Final Technica Report submitted to the BP Conservation Programme-Rufford, pp. 23-25.
  • A. Wakid (2007). Report on the initiatives to involve the major stakeholders of Assam in the conservation of Gangetic dolphin, pp. 45-50.
  • A. Wakid (2009). Status and distribution of the endangered Gangetic dolphin (Platanista gangetica gangetica) in the Brahmaputra River within India in 2005. Current science, 97(8), pp. 1143-1144.
  • A. Wakid and G. Braulik (2009). Protection of endangered Gangetic dolphin in Brahmaputra River, Assam, India. Final report to IUCN-Sir Peter Scott Fund, p.44.
  • R.K. Sinha (2011). The Ganges River Dolphin, India’s National Aquatic Animal. Centre for Environmental Sciences School of Earth, Biological and Environmental Sciences Central University of Bihar, BIT Campus, Patna,The article is retrieved from
  • R.K. Sinha, S. Behera and B.C. Choudhary (2000). The conservation action plan for the Ganges river dolphin 2010-2020.  National Ganga River Basin Authority Ministry of Environment & Forests Government of India, pp. 15-16
  • R.S.L. Mohan, S.C. Dey and S.P. Bairagi (1998). On a residential dolphin population of the Ganges river dolphin, Platanista gangetica in the Kulsi river (Assam), a tributary of Brahmaputra. Ibid, 95(1), pp.1–7.
  • R.S.L. Mohan, S. C. Dey, S. P. Bairagi and S. Roy (1997). On a survey of the Ganges River Dolphin, Platanista gangetica of the Brahmaputra river, Assam. J.Bombay nat Hist. Soc., 94(3), pp.483-495.
  • S.S. Behera,S. Vivek and H. Singh (2012). Status of higher aouatic vertibrates in the Ganga river. Report Code: 028_GBP_IIT_ENB_DAT_05_Ver_Jun 2012.
  • Small Grant and Department of Environment & Forest, Govt of Assam, 80.
  • T.P. Singh, B.K. Dutta and S.P. Biswas (2010).Endangered River Dolphin Platanista gangetica gangetica Roxburgh 1801and Their Threatened Habitat in the River Barak.  Assam University Journal of Science & Technology: Biological and Environmental Sciences, 6(I), pp.75-81.

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