status of ganges river dolphins (platanista gangetica) in the karnali, mahakali, narayani and sapta...

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MARINE MAMMAL SCIENCE, 10(3):368-375 (July 1994) 0 1994 by the Society for Marine Mammalogy

STATUS OF GANGES RIVER DOLPHINS (PLATANISTA GANGETiCA) IN THE KARNALI,

MAHAKALI, NARAYANI AND SAPTA KOSI RIVERS OF NEPAL AND INDIA IN 1993

The Ganges river dolphin, Platanista gangetica, or susu, is a freshwater dolphin distributed throughout the Ganges/Brahmaputra/Meghna river systems in India, Bangladesh, and Nepal (Jones 1982). The World Conservation Union regards the species as vulnerable (Klinowska 199 1). The total world population has been crudely estimated to be 4,000-5,000 animals, with very small numbers in Nepal (Jones 1982).

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NOTES 369

Susus are normally found downstream of shallow areas or tributary junctions (Kasuya and Haque 1972), alone or, less frequently, in groups of 2-3 (Jones 1982). Smith (1993) observed groups of l-3 susus (mean = 1.38, SD = 0.04, n = 72) in the Karnali River most often in “primary habitats” where convergent streams create an eddy counter-current system in the mainstream flow. Less often the dolphins were found in “marginal habitats” where a sharp upstream bend creates a similar eddy counter-current system but of smaller dimensions.

We conducted census surveys of Ganges susus on the four largest river basins in Nepal: the Karnali, Mahakali, Narayani and Sapta Kosi, during the low water season on 19-25 February, l-3 March, 12-18 March, and 26 March- 3 April, 1993, respectively. All four rivers are located downstream of the Siwalik foothills of the Nepal Himalayas and represent the extreme upstream limits of Ganges river dolphin distribution, as well as the upstream limits of gharial crocodiles (Gavialis gangeticus), smooth Indian otters (Lutra perspicillata), Asian small-clawed otters (Aonyx cinerea), soft-shell turtles (Aspiredetes gangeticus, Chitra indica), and hard-shell turtles (Kachuga spp.).

All four river basins are characterized by: (1) alluvial braided channels; (2) relatively high velocity flows in comparison to downstream waters; (3) large seasonal and year-to-year variations in streamflow and sediment transport; and (4) mixed use riparian areas, with small settlements of subsistence farmers and fishermen frequently on one bank and forested jungle and grassland, contained within national parks or wildlife refuges, on the other bank. At one time all four rivers were open to the Ganges River system, but now are affected by barrages (dates of commission reported in Fig. 1). Barrages are low dams used to divert water for irrigation purposes and flood control. The Narayani and Sapta Kosi rivers are contained behind barrages at the Nepal/India border and the Karnali River behind a barrage located approximately 20 km downstream of the border in Kailashpuri, India. These barrages have isolated wildlife populations from any possible genetic interchange with animals inhabiting downstream waters. Dolphins upstream of the barrage may move downstream through the barrages during flood periods, resulting in a permanent loss of animals to an already fragmented population. The barrages also block the movement of migratory fish to spawning streams of the Himalayan foothills. The Mahakali River in Nepal is located below a barrage that severely reduces downstream flow.

Surveys were conducted by two teams of researchers simultaneously searching for animals on foot and in dugout canoes and small rowboats on opposite sides of the river. Each team was led by a researcher with previous experience con- ducting river dolphin surveys. The two teams remained in radio contact to coordinate searching effort and avoid double counting the same group of animals.

We covered all river channels greater than 20 cm deep twice, once upstream and once downstream, from the respective downstream barrages to the uppermost limits of dolphin distribution, evidenced by impassable rocky barriers and/or rapids. The exception was the Mahakali River, which we surveyed only once, downstream, from the upstream barrage to the Nepal/India border.

Because of the low number of dolphins reported in Nepal (Shrestha 1989),


370 MARINE MAMMAL SCIENCE, VOL. 10, NO. 3, 1994

i-b d l.l-7 8:‘E TIBET

INDIA Nat-c

Ri\

Dates of commission for W.I Mahakali Karnali Narayani SaF

28ON

1929 1976 1970 1965

- = Barrage

Figure 1. Map of Nepal showing the Mahakali, Karnali, Narayani, and Sapta Kosi River Basins with an insert reporting the dates of commission of the respective barrages.

and following the recommendations of a panel of experts (Perrin and Brownell 1989), we used a direct count survey method to estimate dolphin numbers. When dolphins were sighted, we remained in the area for approximately 15 min before recording best, high, and low estimates of the number of animals in the group. The high and low estimates were used to reflect our confidence in the accuracy of the best estimate. The low estimate was considered to be an absolute minimum count and the high estimate an absolute maximum count. We used identical best, high, and low estimates to indicate a high level of confidence in our best estimate. During some sightings dolphins appeared to follow the boat, which added uncertainty to whether subsequent sightings were new or the same animal(s). In this case we used a low estimate of zero to reflect the possibility of making double counts.

Long dive times, unpredictable movements, and quiescent behavior also made using a single count unreliable. During quiescent behavior dolphins surface without an audible blow and expose only the uppermost dorsal surface of the melon. Sightings that could not be substantiated by subsequent surfacings or confirmation by a second member of the team were given a best and low estimate of zero and a high estimate of one. We also used distinctive physical characteristics of individual animals (e.g., scarring, length of rostrum relative to the height of melon, and body size) and the location of surfacings relative to shoreline features or other animals to assist in making group-size estimates. Estimates were arrived at by consensus among the team of observers that initially sighted the dolphins.


NOTES 371

Karnali River

(Planned site of

Location of -+ Dolphin Sighting o/knl~ - CtroP..ml

National Park

28’3O’N

Kaurali I I ..I,- 0 , Ghat ” 3o N

Kauri Khola

L Khola

- Kotia Ghat II”““‘* ‘.

\ ‘I..

Figure 2. Map of Kamali Rivet Basin showing locations of dolphin sightings.

Observations were tallied from the two boats to arrive at our estimate of the total number of dolphins for each river.

Although search effort was maintained continuously along the total length of the river, we stopped along the shoreline and searched for dolphins for at least 15 min in areas that had similar physiographic and hydrologic features of


372 MARINE MAMMAL SCIENCE, VOL. 10. NO. 3, 1994

Table 1. Number of dolphin groups sighted and best, high, and low estimates of the total number of dolphins observed during census surveys of the Karnali, Mahakali, Narayani and Sapta Kosi Rivers conducted from 19-25 February, 1-3 March, 12-18 March and 26 March-3 April 1993, respectively.

Upstream survey Downstream survey

Number Total dolphins observed Number of of Total dolphins observed

groups Best High Low groups Best High Low River observed estimate estimate estimate observed estimate estimate estimate

Karnali 14 25 30 21 9 19 20 14 Mahakali - - - - 0 0 0 0 Narayani Sapta Kosi

: : 2 1 1 1 1 3

: 2 2 2 2

previously identified locations of dolphin occurrence. These included eddy counter-current systems downstream of convergent streams and channel meanders (Smith 1993), and areas of slow moving water downstream of deposition islands (identified during a preliminary survey of the Karnali River, 17-18 February 1993, from Prono Ghat to the Kailashpuri Barrage (Fig. 2). We also spent additional time searching for dolphins downstream of natural sandstone and man-made flood control dikes that created eddy counter-current systems similar to those located downstream of convergent streams and channel meanders. Additional time was spent in these areas to avoid missing extremely quiescent or long-diving animals.

The bias between upstream and downstream counts (Table 1) should caution researchers on the reliability of downstream surveys for making absolute estimates of river dolphin populations. The rate of downstream travel by boat, especially in upstream areas, is probably too fast to account for long dive times and quiescent behavior.

The results of these surveys indicate nonviable populations of dolphins in the Mahakali, Narayani, and Sapta Kosi rivers and a marginally viable (?) population in the Karnali River. We believe that the number of animals missed during the surveys is minimal and that the implications of these surveys are valid regardless of the possibility of a few additional dolphins.

No dolphins were observed in the section of the Mahakali River that flows through Nepal. During the low-water season there is not enough water released by the upstream barrage to support river dolphins (a maximum depth of 20 cm in some cross-sections). Local villagers report that dolphins are sometimes seen in the Mahakali just below the Nepal/India border during the monsoon season.

Dolphins inhabiting the Narayani and Sapta Kosi rivers clearly do not represent viable populations, Since new immigrants are blocked by barrages at the Nepal/India border, we consider these populations to be doomed to extinction. The dolphins inhabiting these rivers may have more value as source animals for translocation efforts to augment the marginally viable population in the Karnali


NOTES 373

Table 2. Summary of dolphin sightings on the Geruwa branch of the Karnali River during upstream and downstram surveys in February 1993.

Group Date Time sizea Location

Upstream survey 19 9:43 l-l-l 19 lo:06 1-2-l 19 10:31 l-l-l 19 lo:42 6-8-6 19 11:OO 4-4-2 19 15:02 l-l-l 19 15:33 2-2-2 19 16:24 l-l-l 19 16:45 1-1-O 19 17:09 l-l-l 20 8:30 3-3-2 20 9:40 O-2-0 20 lo:58 2-2-2 20 15:lO l-l-l

Between Kailashpuri Barrage and Kaurali/Geruwa confluence Slightly upstream of above location Below Geruwa and Kaurali confluence on east side Slightly upstream of above location Mouth of Geruwa Slightly downstream of first depositional island of Geruwa Slightly downstream of Bhawanipur Ghat on west bank Slightly downstream of depositional island below Amabardia Slightly upstream of above location Amabardia Downstream of depositional island above Amabardia Slightly upstream of above location Slightly downstream of Nepal/India border Slightly upstream of Oroi tributary confluence

Total count of dolphins for upstream survey = 25-30-21”

Downstream survey 24 14:32 2-2-l Pronoghat 25 9:3 1 l-l-l Slightly downstream of Nepal/India border 25 9:45 1-1-O Slightly downstream of above location 25 lo:13 4-4-4 Amabardia 25 lo:48 3-3-l Slightly downstream of Amabardia 25 11:33 2-3-2 Downstream of Maila tributary convergence 25 14:22 l-l-l Downstream of Katrina Ghat 25 15:06 l-l-l Upstream of Geruwa mouth near convergence 25 15:45 2-2-2 Slightly downstream of pillar post above barrage

Total count of dolphins for downstream survey = 19-20-14”

a Numbers listed in order of Best-High-Low estimates.

River. Long-term programs for rehabilitation of riverine habitat may allow for future reintroductions. Programs for translocating dolphins should consider possible phenotypic differences between populations and be approved by the IUCN Cetacean Specialist Group before being implemented.

With judicious management, dolphins inhabiting the Geruwa Branch of the Karnali River (water levels were not sufficient to support dolphins in the KauraIi Branch with a maximum depth of less than 20 cm in some cross-sections) may have the potential to be a viable population (Table 2 and Fig. 2). Since the low estimate of the upstream count was greater than the high estimate of the downstream count, the upstream count can be considered to be a more accurate estimate of total abundance.

Although the total number of dolphins observed in the Karnali River is encouraging, the apparent decline in the number of dolphins observed above the Nepal/India border and their upstream range is reason for concern. During census surveys conducted in January 1983, Shrestha (1989) recorded 20 dol-


374 MARINE MAMMAL SCIENCE, VOL. 10, NO. 3, 1994

phins upstream of the Nepal/India border with a range extending to Kachali (located approximately 15 km upstream of Chisapani). During census surveys conducted in January and April 1990, Smith (1993) recorded a maximum of seven dolphins upstream of the Nepal/India border with a range extending to Ghosti Ghat (located approximately 2 km upstream of Prono Ghat and 30 km downstream of Chisapani). During our surveys only one or two dolphins were observed upstream of the Nepal/India border and the upstream range of dolphins was limited to Prono Ghat. All three surveys were conducted during the dry season, so it is unlikely that streamflow-related migrations could account for the decline in the number of animals observed upstream of the border and in the range of distribution.

We consider the metapopulation inhabiting the Karnali River to be of special conservation value because: (1) the close proximity of these dolphins to Royal Bardia National Park in Nepal makes them a valuable economic resource for local ecotourist development; (2) preservation efforts aimed at maintaining the viability of a small isolated population of Ganges river dolphins are likely to yield useful knowledge for developing effective strategies for preserving more critically endangered river-dolphin species, the baiji, Lipotes vexillifer, and Indus river dolphin, Platanista minor; (3) preliminary indications of behavioral observations made by one of the authors in 1990 (B.D.S.) indicate that dolphins inhabiting the Karnali River may have developed unique phenotypic patterns of behavior and habitat use as an adaptive response to the local conditions of an upstream environment (e.g., greater energetic constraints of high velocity flows and greater habitat complexity of a braided channel environment); and (4) upstream animals inhabiting relatively uncontaminated waters of the Karnali River might serve as useful ‘controls’ for comparison studies of contaminants in susus from downstream waters of the Ganges system.

Increasing pressures from human use and activities related to geotechnical feasibility studies, and bridge and road construction for the proposed dam in Chisapani, lend a sense of urgency to conserving dolphins in the Karnali River. Alternative development plans that capitalize on the diverse and dynamic nature of the river basin should be considered (Smith 1991). Smaller scale run-of-river hydroelectric projects may be a more environmentally and economically sound strategy (Gyawali 1989). Integral to sustainable conservation plans must be a high priority placed on the economic and social development of subsistence farmers and fishermen living within the river basin environment. Specific recommendations to preserve dolphins in the Karnali River are given in Smith (1993). Other threatened aquatic wildlife species, including the critically endangered gharial crocodile (Thorbjarnarson et al. 1992) have overlapping conservation needs. Collaborative projects to conserve river dolphins and gharial crocodiles, as well as otters and freshwater turtles, would be a wise use of scarce wildlife conservation resources. Shrestha (1989) has proposed an international dolphin sanctuary at the Nepal/India border. This proposal could be expanded to include other endangered aquatic wildlife.

This research was only possible due to the strong support given by the Department of National Parks and Wildlife Conservation in Nepal. Special


NOTES 375

appreciation goes to the Director General, Dr. Tirtha Maskey; Wardens Ram Prit Yadav, Surya Bahadur Pandey, and Ganga Ram Singh; and Ranger Ku1 Bahadur Thapa. Financial assistance was provided by the Whale and Dolphin Conservation Society (WDCS) and Oceanic Society Expeditions (OSE). Assis- tance in the field for the Sapta Kosi Survey was given by Alan and Freida Sherman, Susan Larson, and Bernice Johnson. Logistical help was given by Gajendra Jung Chettri of Menuka Treks and Expeditions. Ang Geltze Sherpa and Ram Bahadur Karki deserve special praise for their unfailing hard work as guides, cooks, and boatmen. A review by Randall Reeves was particularly helpful in improving the manuscript.

LITERATURE CITED

GYAWALI, D. 1989. Water in Nepal, an interdisciplinary look at resource uncertainties, evolving problems and future prospects. Occasional Paper No. 8. East-West Center, Honolulu, Hawaii, 120 pp.

JONES, S. 1982. The present status of the Gangetic susu, Platanista gangetica (ROX- burgh), with comments on the Indus susu, P. minor (Owen). FAO Advisory Com- mittee on Marine Resources Research, Working Party on Marine Mammals, FAO Fisheries Series 5(4):97-l 15.

KASWA, T., AND A. K. M. AMINUL HAQUE. 1972. Some information on the distribution and seasonal movement of the Ganges dolphin. Scientific Reports of the Whales Research Institute 24:109-115.

KLINOWSKA, M. 1991. Dolphins, porpoises and whales of the world: the IUCN red data book. IUCN, Gland, Switzerland.

PERRIN, W. F., AND R. L. BROWNELL, JR. 1989. Report of the workshop. Pages 1-21 in W. F. Perrin, R. L. Brownell, Jr., Zhou Kaiya and Liu Jiankang, eds. Biology and conservation of the river dolphins, occasional papers of the IUCN Species Survival commission, No. 3. IUCN, Gland, Switzerland.

SHRESTHA, T. K. 1989. Biology, status and conservation of the Ganges river dolphin, Platanista gungetica, in Nepal. Pages 70-76 in W. F. Perrin, R. L. Brownell, Jr., Zhou Kaiya and Liu Jiankang, eds. Biology and conservation of the river dolphins, occasional papers of the IUCN Species Survival Commission, No. 3. IUCN, Gland, Switzerland.

SMITH, B. 1991. Can Nepal’s Karnali River dolphin survive? World Rivers Review. 6(2):9, 19.

SMITH, B. 1993. 1990 status and conservation of the Ganges River dolphin (Platanista gangetica) in the Karnali River Nepal. Biological Conservation 66:159-169.

THORBJARNARSON, J., H. MESSEL, F. KING AND J. P. Ross (EDS.). 1992. Crocodiles: an action plan for their conservation. IUCN/SSC Crocodile Specialist Group. IUCN, Gland, Switzerland, 136 pp.

BRIAN D. SMITH, P.O. Box 283, Arcata, California 95521; RAVINDRA K. SINHA, Department of Zoology, Patna University, Patna 800 005 India; UBRAJ REGMI, Royal Chitwan National Park, Kasara, Narayani District, Nepal; KUMAR SAP- KOTA, Kushadevi, Ward No. 2 Kabhre, Bagmati, Nepal. Received 6 December 1993. Accepted 9 March 1994.


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