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The endangered Ganges river dolphins in Nepal: a small and declining population

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SUMMERY The few remaining individuals of the endangered Ganges river dolphin (Platanista gangetica gangetica) are currently limited to only three river systems of Nepal with a best estimate of less than 28 individuals. Reduced concern, lessened awareness and bias investment strategies from stakeholders directly contribute to the process of extirpation, which will lead to further extinction of animals from Nepalese waterways unless meaningful conservation is started. Population abundance and range of distribution has declined sharply in all the river systems of Nepal due to environmental and anthropogenic threats like barrages and regulation of natural flow. Reduced habitat quality (depth and width) in regulated river systems of Nepal during the post monsoon is often below the required minimum threshold, which has magnified the spatial conflict between river dolphin and artisanal fishing communities. A detailed comprehensive management plan for this species is lacking due to limitation of science based rigorous studies. Non invasive and cost effective approaches like photo-ID and acoustics are proposed for this rare and cryptic animal, which improves understanding of the population estimates, ecology and health concerns required to recover this small number of animals in natural habitat of Nepalese river systems. Technical and financial assistance from international communities like the International Whaling Commission and others is imperative for accomplishment of this target.
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The endangered Ganges river dolphins in Nepal: a small and
declining population
Shambhu Paudel*& John L. Koprowski
SUMMERY
The few remaining individuals of the endangered Ganges river dolphin (Platanista gangetica
gangetica) are currently limited to only three river systems of Nepal with a best estimate of less
than 28 individuals. Reduced concern, lessened awareness and bias investment strategies from
stakeholders directly contribute to the process of extirpation, which will lead to further extinction
of animals from Nepalese waterways unless meaningful conservation is started. Population
abundance and range of distribution has declined sharply in all the river systems of Nepal due to
environmental and anthropogenic threats like barrages and regulation of natural flow. Reduced
habitat quality (depth and width) in regulated river systems of Nepal during the post monsoon is
often below the required minimum threshold, which has magnified the spatial conflict between
river dolphin and artisanal fishing communities. A detailed comprehensive management plan for
this species is lacking due to limitation of science based rigorous studies. Non invasive and cost
effective approaches like photo-ID and acoustics are proposed for this rare and cryptic animal,
which improves understanding of the population estimates, ecology and health concerns required
to recover this small number of animals in natural habitat of Nepalese river systems. Technical
and financial assistance from international communities like the International Whaling
Commission and others is imperative for accomplishment of this target.
Keywords: Ganges river dolphin; population; habitat; photo-ID; barrages; international aid
BACKGROUND
The Ganges river dolphin is a well known species since 1980s in Nepal; however profound
scientific and rigorous study is limited. Additionally, species with a very small number often
receive negligible attention from concerned authorities in Nepal when conservation efforts and
investment is biased and donor driven (eg. limited to mega species) given the number of species
in need. As a result, no comprehensive plans for conservation and management of the few
remaining individuals of river dolphin is made to recover population in upstream natural habitat-
Nepal. Limited knowledge on precise population estimates, ecology and interaction with
artisanal fishing practices over several years abated conservation efforts and, could contribute to
threatening process. Understanding the need for conservation of less charismatic species and
their ecological status is imperative to conserve the tiny number of individuals of river dolphins
for future generations in Nepalese river systems. Barrages (large structure builds across the river
to reduce natural flow) constructed across the river systems under the political agreement
between Nepal and India (after 1950s) is a major threat and has created isolated groups of this
species (Fig.1). Barrages were constructed above or below or at the border between Nepal and
India- 20km below border in India of Karnali; 6km above the border in Sapta Koshi of Nepal and
at the border in Narayani river system.
* Institute of Forestry, Tribhuvan University, Pokhara, Nepal
School of Natural Resources & the Environment, University of Arizona, USA
Possible genetic connectivity between Nepal and India populations (Ganges River in India)
remains only in Sapta Koshi River of Nepal because the barrage is above border in Nepal and
large numbers remain only below the barrage in Nepal within span of 6km), however little is
known about this status.
RESULTS:
Population status and range of distribution:
Recent surveys concluded that a total of 28 individuals river dolphins remained in three river
systems of Nepal- Sapta Koshi, Karnali and Narayani, which was calculated by applying wooden
boat based visual count method (Paudel et al. 2015b). In the Koshi River, Shrestha (1993)
recorded 18 individuals both upstream and downstream of the barrage covering a stretch of 54km
(48km upstream and 6km downstream section) in 1989. But Smith (1993) recorded only 3
individuals in a 1990 survey in the upstream section of the river. After a long hiatus of
monitoring, Chaudhary (2007) noticed 15 individuals only in the downstream section, and
complete extirpation of river dolphin from upstream section of the Koshi River. After flood
disaster in Koshi in 2008, Limbu and Subba (2011) recorded 6 individuals in the upstream and 5
individuals in the downstream section of the Koshi River, which was due to varied width of river
Figure 1 Location of dams in Nepal, India and Bangladesh. Yellow circle indicate location of dam in different countries.
system where water did not flow through barrage gates. In recent survey efforts conducted
between 2013-2016, no river dolphins were recorded upstream and the best estimates of 14
individuals were recorded below the barrage area within a span of 6km (Paudel et al. 2015). In
Narayani River, Smith (1993) recorded only one individual with a best estimate of 2 individuals.
A similar finding was made by (Paudel et al. 2015b) after two decades. This single individual
was recorded just 1km from the barrage area (border or barrage area), which may no longer be
available due to lack of lateral connectivity and high flood pressure during monsoon season. No
previous reference was identified for the Narayani River, but key informants mentioned that
dolphins were noticed within a 55km span in the Narayani in recent history with a very good
abundance of river dolphins. In Karnali, Shrestha (1983) recorded approximately 22 individuals
in the 55km span of distribution, however Smith (1993) recorded a maximum of 7 individuals in
Geruwa (tributary of Karnali) during 1990 survey across a range of 30km. A recent study
(Paudel et al. 2015a, 2015b), reveals that a maximum of 5-8 individuals were recorded within a
range of 25km in the Karnali main stream, with no records in Geruwa tributary.
Habitat ecology:
River flow and anthropogenic factors heavily determined the quality of river dolphin habitats.
Naturally changing flow pattern (eg. in Karnali, the Geruwa tributary was previously occupied
by river dolphin but now dolphins are limited to the Karnali main stream because of high volume
of discharge) shifted the distribution and occupancy frequently in both the Sapta Koshi and
Karnali river systems. Influence of the barrage on the distribution and occupancy is marked in
Sapta Koshi River, which directly guided the direction of flow and hence, dolphin distribution
changed abruptly (Fig.2). This may increase stress on their feeding and movement, but further
verification is needed through intense studies. Poor coordination between conservation agencies
Figure 2 Regulated flow in Sapta Koshi.
and barrage administration authority is a major threat to the conservation of remaining
individuals in Sapta Koshi river system. Depth and width of river systems is highly different
between seasons- pre and post monsoon. As a result, mean depth (Karnali: 5.55 ± 4.13m, Sapta
Koshi: 1.40 ± 1.10m, Narayani: 2.65 ± 1.56m) and width (Karnali: 187.16 ± 78.55m, Sapta
Koshi: 258.04 ± 132.59m, Narayani: 197.11 ± 56.36m) of river systems varied significantly.
Interaction between the effects of river systems and season on the depth of river systems was
noticed in Nepal. The depth and width recorded in dolphin inhabited river systems were lower
than the observed threshold for dolphin survival during the post-monsoon period (Akbar et al.
2004, Smith et al. 2008) and, as a consequence, abundance was likely reduced during the post
monsoon compared to the pre-monsoon season in Nepal. River geometry (and geomorphics) and
development structures constructed at the India/Nepal border in all river systems pose the
greatest threat towards the extinction of the river dolphin due to the dramatic changes in river
flow characteristics (Paudel et al. 2014) and reduced habitat that result. Over the past three
decades, abundance and range of distribution were significantly reduced in Nepalese river
systems (Smith et al. 1993; Paudel et al. 2015b). On the other hand, 11 water storage projects
have been identified and proposed in the Koshi Basin (Chinnasamy et al. 2015) and 2 mega
projects (e.g Karnali chisapani multipurpose dam 10800 MW and 900 MW upper Karnali
hydropower) in the Karnali basin. This may reduce current available habitat significantly during
the low water season and may place the remaining individuals at the brink of extinction unless
precise understanding of the ecological water requirement of freshwater river dolphin during low
water seasons is known.
CONSERVATION ISSUES AND THREATS
Inadequate conservation investments in non-charismatic species: The concerned authorities in
Nepal need to focus more effort on less charismatic but critically endangered species with
small populations like river dolphins and not solely invest in mega species like elephant,
rhino, and tiger whose likelihood of survivorship is higher than river dolphins. In
particular, parks field offices must enhance research, monitoring, and management of
endangered river dolphin population in their natural habitat.
Lacking of international collaboration efforts between Nepal and India Government: The river
dolphin is a migratory species, but no efforts have been jointly organized between these
two countries for the conservation of this migratory species. As a result, estimation of
abundance, behaviors and range of distribution in relation to conservation and
management of the remaining population is being affected.
Limited funding opportunity for intensive research: Although data are limited on behaviors
(surfacing and habitat use) and abundance, funding to understand such quantitative
information is limited. Use of recent technologies like acoustics and photo-ID requires
funding and skilled scientists; priority for this area of research is too low by many
international funding agencies. Recent studies with support from international experts in
Nepal revealed that use of photo-ID could be applicable to estimate abundance and
examine health issues in relation to environmental and anthropogenic pressures (Fig.3).
Such a reliable approach should be promoted for this rare and cryptic species through
international aids.
Large development structure: In addition to barrages constructed across the river,
governments have built, proposed and planned several irrigation intakes and hydropower
projects in all of the river systems. This could reduce habitat/range of distribution largely
by reduction or disruption of natural flow, especially during low water season when
habitat is already at a critical stage. Also, spatial overlap between river dolphins and
artisanal fishing communities will be prominent. Quantitative relationships between
development structure and ecology of river dolphins in relation to water requirements
should be explored before construction of large structures to develop management plans
and mitigation strategies.
Interaction between artisanal fishing and river dolphin: Immense pressure is experienced from
artisanal fishing communities in Nepalese river systems that are used for their daily
livelihoods. Fishing in preferred locations is common for both the communities and river
dolphins in Sapta Koshi and Karnali river systems. Two river dolphins were entangled,
which lead to happen dead from fishing communities in last couple of years. Alternative
livelihoods (e.g. provision of seed money for small groups of fishing dependents to adopt
aquaculture; improving river dolphin based tourism activities by strengthening the
capacity of local community’s institutional and networking activities especially including
youth) should be promoted.
Figure 3 Battered and bruised river dolphin recently captured in Sapa Koshi by photo-ID approach
RECOMMENDATION
Regular monitoring of the remaining number of endangered river dolphins using recent
technologies like photo-ID and acoustics is proved to be the best approach in Nepalese river
systems, and these approaches are lacking in Nepal to understand the abundance, distribution
range, habitat use and site fidelity in Sapta Koshi and Karnali river systems of Nepal due to
limitation of funding and technical expertise. An immediate recovery action plan should be
formulated with the support from international communities like IWC and Species Survival
Group (SSG) of IUCN. Quantitative relationships of natural flow in relation to ecology of river
dolphins should be understood before approving water related projects in Nepal. In line with this
scenario, IWC and SSG should encourage government attention to develop and implement
effective conservation actions in the field.
ACKNOWLEDGMENT
We would like to thank Ocean Park Conservation Foundation, Hong Kong and the Rufford
Foundation, UK for their generous support for dolphin research in Nepalese river systems. The
WWF Russell E. Train Fellowship for higher study opportunity in the field of freshwater species
conservation. Special thanks to the International Whaling Commission for the invitation to this
scientific committee meeting to share the work being undertaken with the river dolphins in
Nepal. Sincere thanks to Grant Abel for his photography and technical assistance during the
photo-ID trial and to Dr Lindsay Porter for her encouragement and moral support.
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... The Indus River dolphin occurs only in the Indus River system, the vast majority of individuals occur in Pakistan and a small remnant population estimated as less than 10 animals is present in the Beas River, IndiaWWF-India 2018). The Ganges River dolphin has a much larger range than the Indus subspecies, occurring in many rivers in India and Bangladesh and also in small numbers in some of the rivers in southern Nepal(Paudel et al., 2017). barrages. ...
... Dolphins in Nepal occur in very small numbers in three rivers (Karnali, Narayani, Koshi), a declining trend has been observed and there is complete extirpation from some upper river segments. Barrages on the India-Nepal border might prevent their dispersal into India(Smith et al., 1994;Paudel & Koprowski 2017). ...
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Ex situ options for cetacean conservation a d a w n o f h o p e c ri tically en d a n g e r e d e x t i n c t endang e re d v u ln erable
... The Indus River dolphin occurs only in the Indus River system, the vast majority of individuals occur in Pakistan and a small remnant population estimated as less than 10 animals is present in the Beas River, IndiaWWF-India 2018). The Ganges River dolphin has a much larger range than the Indus subspecies, occurring in many rivers in India and Bangladesh and also in small numbers in some of the rivers in southern Nepal(Paudel et al., 2017). barrages. ...
... Dolphins in Nepal occur in very small numbers in three rivers (Karnali, Narayani, Koshi), a declining trend has been observed and there is complete extirpation from some upper river segments. Barrages on the India-Nepal border might prevent their dispersal into India(Smith et al., 1994;Paudel & Koprowski 2017). ...
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Chapter
The South Asian River dolphin (Platanista gangetica) consists of two subspecies, the Indus (Platanista gangetica minor) River dolphin endemic to the Indus River system primarily in Pakistan and the Ganges (Platanista gangetica gangetica) River dolphins which occurs only in the Ganges, Brahmaputra and Karnaphuli-Sangu River systems of India, Bangladesh and Nepal. The species, and both subspecies are classified as Endangered on the IUCN Red List. The Indus River dolphin is thought to number approximately 2000 individuals, fragmented into 5 different sections of river, and the species has undergone an 80% reduction in range. Since a ban on the hunting of dolphins in the 1970s the dolphin population has been increasing in abundance. The Ganges dolphin is more numerous than the Indus dolphin, has a wider range and has suffered a less drastic range decline, however the threats from fishing, high levels of industrial pollution, shipping, poaching, habitat fragmentation by barrages, flow regulation due to hydropower generation and flow depletion from diversions for irrigation suggest that its population is declining. The Indian Waterways project and proposals to link Indian river systems may cause rapid catastrophic declines in the subspecies in the future if they proceed. Platanista are not currently held in captive facilities anywhere in the world. In the 1970s a total of 16 Platanista were maintained in international captive facilities, 4 at the Steinhart Aquarium in the USA (Indus dolphins), 7 at the Berne Institute of Brain Anatomy in Switzerland (Indus dolphins) and 5 at Kamogawa Sea World in Japan (Ganges dolphins). Survivorship was poor, ranging from a few weeks up to approximately 3 years and no breeding ever occurred. A variety of rescue programmes to capture and translocate Platanista from canals and channels suggest that this species is relatively robust to capture and transport, however suspected capture myopathy has occurred in a number of individuals. There is very little technical or infrastructure capacity for holding captive cetaceans in South Asia at present, the quality of care and husbandry in most zoos is extremely poor, and in India the keeping cetaceans in captivity for entertainment has been prohibited.
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