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Chapter… The status and distribution of freshwater fishes
of Eastern Himalayan region
X.1
Overview of Eastern Himalayan fish fauna
Abell et al. (2008) presented a global map
consisting of 426 freshwater ecoregions based
on the distributions and compositions of
freshwater fish species. This will be useful for
global and regional conservation planning
efforts. According to Abell et al., the Eastern
Himalayas consists of seven freshwater
ecoregions (see Fig. XXX (map of EH
ecoregions will be shown in the intro chapter);
they are: Ganges delta and plain, Ganges
Himalayan foothills, Upper Brahmaputra,
Middle Brahmaputra, Chin Hills-Arakan
coast, Sittang-Irrawaddy and Inle lake. They
also showed that the region has species
richness consisting of about 500 fish species.
The Irrawaddy ecoregion is shown to have
119-195 endemic species while the Ganges
delta and plain to have 28-40 species. Kottelat
& Whitten (1996) estimated the Ganges River
drainage to contain 350 and Brahmaputra and
Irrawaddy river drainages to contain 200
species of fishes respectively.
X.1.1
Fig. 1 Freshwater ecoregions of the Eastern
Himalayas (redrawn after Abell et al, 2008)
Geomorphological factors affecting distribution of the eastern Himalayan fishes
The region under assessment is the Eastern Himalayas aquatic biodiversity hotspot and should not be
confused with the biodiversity hotspot of Myers et al (2000) and Roach (2005) which are based on
terrestrial flowering plants. The present area of assessment consists of the Himalaya and a part of
Indo-Burma terrestrial hotspot. Kottelat & Whitten’s (1996) map of ‘hot spots’ for freshwater
biodiversity in Asia based on fishes also included major parts of northeastern India and Myanmar.
1996)
The Eastern Himalayas is a biodiversity rich bioregion. The diversity is attributed to the recent
geological history (the collision of Indian, Chinese and Burmese plates) and the Himalayan orogeny
which played an important role in the speciation and evolution of groups inhabiting mountain streams
(Kottelat, 1989). The evolution of the river drainages in this part of the world has been the subject of
several studies that utilize geological evidence to reconstruct the paleodrainage patterns during much
of the Cenozoic (Brookfield, 1998; Clark et al., 2004). Studies on the molecular phylogeny of the
fishes of this region (e.g. Rüber et al., 2004; Guo et al., 2005) have indicated that vicariant-based
speciation has played a substantial role in shaping the current distribution pattern of the fishes.
The fish fauna of the Eastern Himalayas region may be subdivided into three drainage-based
geographic units:
1.
The Ganges-Brahmaputra drainage, which flows in the Ganges Himalayan foothills,
Ganges Delta and Plain ecoregions and Upper and Middle Brahmaputra;
2.
The Chindwin-Irrawaddy drainage in the Sittang Irrawaddy freshwater ecoregion
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3.
X.2
The Koladyne (Kaladan) drainage and the short drainages along the western face of the
Rakhine Yoma of Myanmar in the Chin Hills-Arakan freshwater ecoregion. There is
considerable endemicity in the freshwater ichthyofauna of this region.
Conservation status (IUCN Red List Criteria: Global Scale)
Half of the fish species (263 species out of 523) in the Eastern Himalayas (50.3%) are categorized as
Least Concern (LC) (Fig. 2). These fishes are distributed mostly in the Indo-Gangetic Plains, deltaic
regions of Bangladesh, lower Assam plains and northern parts of Arunachal Pradesh and its adjoining
areas in China (Fig. 3). Although the Indo-Gangetic Plains is one of the most densely populated areas
in the Indian subcontinent, many of the fish species assessed as Least Concern are either distributed
widely enough, or their population sizes are believed to be large enough. One one or both of these
features are believed to buffer the populations from any adverse effects due to anthropogenic threats.
Even so, empirical data to strongly support their assessment status is lacking for a number of these
species; in such cases, the assessment as Least Concern is more often based on perceived abundance
from sampling data. Even so, some of these species currently assessed as Least Concern may require
reassessment in the future, given that they are suspected to belong to species complexes containing
several morphologically similar (cryptic) species having more geographically circumscribed ranges
(one such example is Aplocheilus panchax).
The next highest number of species
(27%) in the Red List category is
Eastern Himalayas Fish overall threat status
Data deficient. The species in this
category possess one or more of the
DD, 27.2, 27%
following features: 1. Small body
size, with little commercial value
CR
EN
(either as food or as ornamental
VU
fishes); 2. Very recent recognition as
LC, 50.3, 50%
NT
distinct taxonomic entities; 3.
CR, 1.0, 1%
LC
EN,
3.1,
3%
Known only from the type series
DD
and/or very scanty museum records;
VU, 9.8, 10%
4. Little or no information on their
biology; 5. Taxonomic uncertainties
NT, 8.8, 9%
surrounding the identity of these
species, typically belonging to Fig. 2. The proportion of fish species in each Red List Category
species complexes of very similar- in the eastern Himalayan region
looking forms. For all these groups,
there are no data on their occurrence, population trend etc. A detailed discussion of the issues
surrounding the data deficiency is provided in section X.3.
A total of 72 species (13.9%) are categorised as threatened while 46 (8.8%) as Near Threatened. The
five critically endangered species (1.0 %) are all endemic to hill streams, lake and cave. Out of the 16
endangered species 10 are endemic in the Ganges-Brahmaputra, four in the Chindwin and one in the
Inle Lake. One species, Clarias magur is common to both the drainages.
Table. The number of fish species and percentages of Eastern Himalayan fishes under IUCN
Red List category
Red List Category
CR
EN
VU
NT
LC
Number of Species
5
16
51
46
263
2
Percentage
1.0
3.1
9.8
8.8
50.3
DD
Grand Total
142
523
3
27.2
100.0
X.3
Patterns of species richness
X.3.1
All fish species
The Brahmaputra basin in Arunachal Pradesh, Meghalaya, northern Bengal together with parts of
Assam and Himalayan foothills between Nepal and Uttar Pradesh contain most diverse fish fauna
(Fig. 3). Species richness is seen in the Tista, Kameng, Dikrong, Subansiri and Siang basins. The
richness in these areas is due to the diversity of habitats and environment existing between the plains
of the Brahmaputra at a low altitude (say 120-200 m asl) to the upland coldwater regions (say 1,5003,500 masl) in the hill ranges in Arunachal Pradesh and also in Meghalaya and Assam within a short
aerial distance of 200-500 kilometres.
Fig. 3
Map showing
species richness in
the eastern
Himalayan region
Fig. 4
Map showing
Endemic Species
richness in the
eastern Himalayan
region
The richness is expected in other basins, viz., the Lohit and Dibang basins and those in Bhutan
flowing to the Brahmaputra drainage and headwaters of the Barak and Chindwin basins and the
Koladynedrainage. The KoladyneRiver is a drainage that flows between the Ganges-Brahmaputra and
the Chindwin-Irrawaddy drainages. The river is separated from the Ganges-Brahmaputra drainage by
the Chittagong hill tract in the west and from the Chindwin-Irrawaddy by the Rakhine Yoma hill
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range in the east; it is not, however, connected to either of these, even in the floodplains. The
ichthyofauna of the Koladyne is poorly explored (Anganthoibi and Vishwanath 2010). Inaccessibility
and differences in sampling intensities might be the reasons for not reflecting these areas in the map.
The drainage is in the Chin
Hills-Arakan
ecoregion.
Although Kar and Sen (2007)
listed 42 species of fishes from
Kaladan, they neither gave
descriptions of the species nor
mentioned where the collections
are deposited. Our recent
collections show that the river
has a diverse ichthyofauna
(Anganthoibi & Vishwanath,
2009, 2010a & b), which may be
under
considerable
anthropogenic pressure.. Further
habitat modification and (most
likely) degradation is to be
expected in this river drainage
with the proposal for the
Kaladan
(Koladyne)
Multipurpose project, which involves the creation of inland waterways to enable navigation from the
port of Sittwe in Myanmar to the state of Mizoram in northeastern India through the river for supply
of essential commodities from mainland India.
We recognize that the areas of high diversity indicated here may reflect a research and sampling bias,
since the ichthyofauna of the areas with the highest densities have been the subject of numerous
recent studies (e.g. Ng, 2006; Vishwanath & Linthoingambi, 2007). It is likely that the diversity of
the ichthyofauna of the Indo-Gangetic Plains may be higher than currently recognized. However,
given the paucity of hillstream taxa in the plains, this diversity is not likely to be higher than that of
the area identified here (i.e. the northeastern corner of the Indian subcontinent). The northern parts of
the region under study are occupied by the Himalayas where the fish diversity is lower because of the
high altitude and cold temperature.
X.3.2
Threatened species
The most threatened fishes are in the Chindwin basin in Manipur (Fig. 6), particularly the Imphal
River and its tributaries draining the surrounding hills and the central plain of Manipur and the
adjoining areas in Myanmar, i.e., the eastern parts of the Chin Hills and the Kabaw valley. The Barak
basin in Manipur is also under threat. The other areas of threat of lesser magnitude are: Brahmaputra
Fig. 6
Map showing
threatened
species richness
in the eastern
Himalayan
region
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basin in parts of Arunachal Pradesh, Upper Assam, Meghalaya, Tista basin in Sikkim and northern
Bengal and Western Nepal.
Imphal River and its tributaries form a part of the Chindwin headwaters. All the hills of Manipur are
at a height of about 1,500-2,500 m asl while the Myanmar plains where Chindwin flows is at a much
lower altitude (Kabaw valley is at 300 masl) providing limited range for distribution. There are many
hill stream fishes endemic to Manipur.
While siltation has caused drying up of many swamps which have been reclaimed either for paddy
cultivation or encroachment of land for expansion of residential areas, the commissioning of Loktak
hydro-electric project in 1983 has caused drastic change in the aquatic environment in the basin. The
Loktak lake (about 40,000 ha), the largest freshwater lake in north eastern India is fed by several
streams. The lake is drained into the Imphal River by the Ithai stream. To supply water required for
the hydro-electric project from the lake, a barrage has been constructed across the Imphal River
slightly below the point where the Ithai stream joins the Imphal River. Thus water brought by the
Imphal River is fed into the lake by reversing the flow of the Ithai.
In addition, there are threats to the fishes in hill streams due to destructive fishing. Brahmaputra
drainage is widely spread and species may find other alternative basins in the drainage for their
survival. On the other hand Imphal river basin with restricted boundaries remains isolated and thus
there is great threat. With the construction of the barrage, the upstream and downstream sections of
the Imphal River, the main drainage of the Manipur valley are fragmented.
With the development of Moreh (Manipur, India) and Tamu (Myanmar) townships for Indo-Myanmar
trade, there is great increase in human population and development activities. This has also caused
threat to aquatic environment, particularly in the Lokchao River in Manipur and Yu river basin in
Myanmar.
Out of the 16 endangered species, Puntius manipurensis Menon, Rema Devi & Vishwanath, 2000;
Schistura kanjupkhulensis (Hora, 1921) and Psilorhynchus microphthalmus Vishwanath &
Manojkumar, 1995 are endemic to Manipur valley while Schistura reticulata, in the eastern hill
streams of Manipur draining into the Yu River.
Out of the 51 species categorized as
vulnerable,
28
species
are
distributed in the Chindwin basin in
Manipur and adjoining areas. While
Myersglanis blythii (Day, 1870) is
found only in the Tista basin in the
Fig. 7. Meyersglanis jayarami Vishanath & Kosygin, 1999
Darjeeling Himalayas and presently
categorized as Data Deficient, the
only other congener, M. jayarami Vishwanath & Kosygin, 1999 (Fig. 7) is endemic to the Chindwin
basin in Manipur and is vulnerable.
Table … List of species categorized as Vulnerable and their distribution
Species
Distribution
Aborichthys garoensis Hora, 1925
Aborichthys tikaderi Barman, 1985
Bangana almorae (Chaudhuri, 1912)
Brahmaputra
Brahmaputra
Brahmaputra
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Barilius chatricensis Vishwanth & Selim, 2002
Barilius dimorphicus Tilak & Hussain, 1990
Barilius dogarsinghi Hora, 1921
Barilius ngawa Vishwanath & Manojkumar, 2002
Botia rostrata Gunther, 1868
Cirrhinus cirrhosus (Bloch, 1795)
Danio jaintianensis Sen, 2007
Devario acuticephala (Hora, 1921)
Devario anomalus Conway, Mayden & Tang, 2009
Devario assamensis (Barman, 1984)
Devario browni Regan, (1907)
Devario naganensis (Chaudhuri, 1912)
Devario yuensis (Arunkumar & Tombi Singh, 1998)
Garra bispinosa Zhang, 2005
Garra compressus Kosygin Singh & Vishwanath, 1998
Garra flavatra Kullander & fang, 2004
Garra litanensis Vishwanath, 1993
Garra manipurensis Vishwanath & Sarojnalini, 1988
Garra nambulica Vishwanath & Joyshree, 2005
Garra paralissorhynchus Vishwanath & Shanta Devi, 2005
Glyptothorax manipurensis Menon, 1955
Gymnocypris dobula Gunther, 1868
Gymnocypris scleracanthus Tsao, Wu, Chen & Zhou, 1992
Laubuca khujairokensis (Arunkumar, 2000)
Myersglanis jayarami Vishwanath & Kosygin, 1999
Nemacheilus pavonaceus (McClelland, 1839)
Physoschistura elongata Sen & Nalbant, 1982
Pseudecheneis sirenica Vishwanath & Darshan, 2007
Pseudecheneis ukhrulensis Vishwanath & Darshan, 2007
Puntius ater Linthoingambi & Vishwanath, 2007
Puntius chelynoides (McClelland, 1839)
Puntius jayarami Vishwanath & Tombi Singh, 1986
Puntius khugae Linthoingambi & Vishwanath, 2007
Puntius ornatus Vishwanath & Juliana, 2004
Puntius shalynius Yazdani & Talukdar, 1975
Puntius yuensis Arunkumar & Tombi Singh, 2003
Rasbora ornatus Vishwanath & Laishram, 2005
Semiplotus semiplotus (McClelland, 1839)
Schistura chindwinica (Tilak & Hussain, 1990)
Schistura inglisi (Hora, 1935)
Schistura khugae Vishwanath & Santa, 2004
Schistura nagaensis (Menon, 1987)
Schistura prashadi (Hora, 1921)
Schistura reticulofasciata Singh & Banarescu, 1982
Schistura singhi (Menon, 1987)
Schizothorax richardsonii (Gray, 1832)
Sisor barakensis Vishwanath & Darshan, 2005
Yunnanilus brevis (Boulenger, 1893)
Brahmaputra
Brahmaputra
Chindwin
Chindwin
Brahmaputra
Brahmaputra
Brahmaputra
Chindwin
Brahmaputra
Brahmaputra
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Chindwin
Brahmaputra
Brahmaputra
Chindwin
Chindwin
Brahmaputra
Brahmaputra
Brahmaputra
Chindwin
Chindwin
Ganges
Chindwin
Chindwin
Chindwin
Brahmaputra
Chindwin
Chindwin
Brahmaputra
Brahmaputra
Brahmaputra
Chindwin
Chindwin
Chindwin
Brahmaputra
Brahmaputra
Ganges
Brahmaputra
Chindwin
The Barak basin in Manipur is also shown in the threat map. The western hills of Manipur are drained
by the Barak and its tributaries. The river flows southwards on the eastern side of the Vangai range
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and then makes a U-turn at Tipaimukh where it is joined by the Tuivai River, flowing westward
between Manipur and Myanmar. The Barak then flows northward on the western side of the Vangai
range and then enter the Cachhar district of Assam to finally enter Bangladesh and join the SurmaMeghana basin. With the upcoming of the Tipaimukh High Dam for the hydro-electric project, there
will be flow modification and flooding of the Barak basin in the western part of Manipur. Habitats of
several hill stream fishes will be disturbed and upstream and downstream parts of the river will be
fragmented.
Species endemic to Barak basin of Manipur, viz, Badis tuivaiei Vishwanath & Shanta, 2004;
Pterocryptis barakensis Vishwanath & Sharma, 2006; Schistura minutus Vishwanath & Shantakumar,
2006 and S. tigrinum Vishwanath & Nebeshwar, 2005 have been categorized as endangered and Sisor
barakensis Vishwanath and Darshan 2005, as vulnerable.
Table. List of endangered fish species and their distribution
Species
Amblyceps arunchalensis Nath & Dey, 1989
Badis tuivaiei Vishwanath & Shanta, 2004
Clarias magur (Hamilton, 1822)
Devario horai (Barman, 1983)
Lepidocephalichthys arunachalensis (Datta & Barman, 1984)
Mastacembelus oatesii Boulenger, 1893
Pillaia indica (Yazdani, 1972)
Psilorhynchus microphthalmus Vishwanath & Manojkumar, 1995
Pterocryptis barakensis Vishwanath & Sharma, 2006
Puntius manipurensis Menon, Remadevi & Vishwanath,2000
Schistura kangjupkhulensis(Hora, 1921)
Schistura minutus Vishwanath & Shantakumar, 2006
Schistura reticulata Vishwanath & Nebeshwar, 2004
Schistura sijuensis (Menon, 1987)
Schistura tigrinum Vishwanath & Nebeshwar, 2005
Tor putitora Hamilton, (1822)
Distribution
Brahmaputra
Brahmaputra
Ganges-Brahmaputra
Brahmaputra
Brahmaputra
Inle Lake
Brahmaputra
Chindwin
Brahmaputra
Chindwin
Chindwin
Brahmaputra
Chindwin
Brahmaputra
Brahmaputra
Ganges-Brahmaputra
The critically endangered species constitute only one per cent of the assessment. Of the five species of
the category, one sisorid catfish, Glyptothorax kashmirensis Hora, 1923 is restricted to Kashmir
valley and three schizothoracines, viz., Schizothorax integrilabiatus (Wu et al, 1992), S. nepalensis
Terrashima, 1984 and S. rarensis Terrashima, 1984 to high altitude lakes, the first one to the Xixong
Lake, Tibet, China, and the later two to the Rara lake, Nepal. One neacheiline loach, Schistura
papulifera Kottelat et al, 2007 (Fig. 8) is endemic in the Krem Synrang Pamiang cave system, in the
Jaintia Hills, eastern Meghalaya, India. Looking at the several threats occurring in this area, more
numbers of species are expected to fall under in this category. Since no sufficient data are available
from remote areas as these have not been visited by ichthyologists, we can not comment at the
moment. However, it is fact that Eastern Himalayan region is very rich in fish diversity as it is shown
by the continuing discovery of new species. Surveys are required to assess the population and threat
status of such fishes. It is required to solve taxonomic ambiguities of many nominal species.
Taxonomy has been given least importance and attentions are being paid more to research for the
production of high yielding fish varieties to meet the ever increasing demands of food fishes.
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Fig. 8. Schistura papulifera Kottelat,
Harries & Proudlove, 2007 [photo
courtesy: Maurice Kottelat]
Table…. List of Critically endangered fishes and their distribution
Species
Glyptothorax kashmirensis Hora, 1923
Schizothorax integrilabiatus (Wu et al, 1992)
Schizothorax nepalensis Terashima, 1984
Schizothorax raraensis Terashima, 1984
Schistura papulifera Kottelat, Harries & Proudlove, 2007
Distribution
Kashmir valley
Xixong lake, Tibet, China,
Rara Lake, Nepal
Rara Lake, Nepal
Krem Synrang Pamiang cave system,
Meghalaya, India
Out of the 16 species assessed as endangered, Badis tuivaiei Vishwanath & Shanta, 2004, Schistura
minutus Vishwanath & Shantakumar, 2006, S. tigrinum Vishwanath & Nebeshwar, 2005 and
Pterocryptis barakensis Vishwanath & Nebeshwar, 2006 are known only from the Barak basin in
Manipur (Surma-Meghana river system). The upcoming Tipaimukh dam across the river Barak is
causing loss of habitat to the species. The distribution of B. tuivaiei which is known from the Barak
and one of its tributaries, the Tuivai, will be fragmented with this dam. Schistura reticulate
Vishwanath & Nebeshwar, 2004, S. kanjupkhulensis and Psilorhynchus microphthalmus Vishwanath
& Manojkumar, 1995 of the Chindwin headwaters of Manipur are suffering habitat loss due to sand
and gravel mining for building constructions and urban development near their habitats. Schistura
sijuensis Menon, 1987 is a cave fish restricted to the Siju cave in Meghalaya. Puntius manipurensis is
endemic to Lokatak lake, a Ramasar site, the largest freshwater lake and in north-eastern India. The
Ithai barrage constructed across the effluent of the lake to retain water for the Loktak Hydro-electric
project and eutrophication has caused intensive damage to the ecology of the lake. The species listed
by Hora (1921) are not to be seen. Many weed fishes and introduced fishes, mostly Chinese carps,
Oreochromis mossambicus (Peters, 1852) and Clarias gariepinus (Burchell, 1922) have substituted
the endemic species.
We need to confirm the generic status of Lepidocephalichthys arunachalensis (Datta & Barman,
1984) which they originally described under genus Noemacheilus. Kottelat (1990) doubted the
inclusion of the species under the genus the authors affiliated and suggested for inclusion under genus
Lepidocephalichthys based on the author’s illustrations. The species is presently assessed as
endangered. More surveys are required to find out the present distribution of Mastacembelus oatesii
Boulenger, 1893, Devario horai (Barman, 1983), Pillaia indica (Yazdani, 1982). Clarias magur
(Hamilton, 1822) has been resurrected from synonymy with C. batrachus (Linnaeus, 1758) by Ng &
Kottelat (2008). All the available literature shows the collections of the genus from eastern Himalayan
region as C. batrachus. Thus more detailed examination is required to see the actual range of
distribution of the species.
Out of the species assessed as vulnerable, two species, often termed as ‘king fish’ viz., Semiplotus
semiplotus of the Ganges-Brahmaputra and Semiplotus modestus of Koladyne basins deserve special
attention. Semiplotus has a unique oral morphology consisting of an inferior, broad mouth with an
exposed cornified mandibular cutting edge and a dentary with a broad deflected labial surface. It is
9
used to scrap algae on the bottom rocks. The fishes migrate upstream in shoals at night feeding on the
algae on bottom rocks. Destruction of habitat, feeding grounds of the species will be a great pressure
to their existence.
Restricted range/endemic species
The Eastern Himalayas is an area of considerable endemicity in its freshwater ichthyofauna. Much of
this endemicity stems from the presence of numerous hillstream species with highly restricted
distributions (e.g. many members of the Balitoridae and Sisoridae). This endemicity is largely due to
vicariant speciation brought about by the orogeny of the Himalayan region (He et al., 2001; Rüber et
al., 2004). All known species of the genus Aborichthys are endemic to Brahmaputra drainage in
northern Bengal, Meghayala and Arunachal Pradesh. Several species of Amblycipitidid and Sisorid
catfishes, danionins, badids are also endemic to Brahmaputra drainage.
Fig. 9. Aborichthys sp. (collected from Dikrong
River, Arunachal Pradesh, Photo: W.
Vishwanath)
(endemicity) Endemic fishes of Manipur. The collections of fishes from Manipur by Hora
(1921) have been grouped under two: those from northern watershed and from southern watershed,
which in fact belong respectively to the Brahmaputra and Chindwin basins. He remarked that the
southern watershed fauna consisted of Burmese and endemic Manipur elements. Hora & Mukerji
(1935) also reported that the fish fauna of Naga hills (Naga Hills of British India consists of parts of
the present Nagaland and Manipur) contain both Assamese (Brahmaputra) and Burmese (Chindwin)
elements in equal proportions.
Endemic fishes of Brahmapura basin. ……………………
Data Deficient species
About 27 per cent of 525 species of fishes are assessed as Data Deficient. Given this relatively high
percentage of species assessed as such, it is necessary to examine the underlying reasons for the lack
of information in greater detail. Approximately half (74 out of 142) of the species assessed as Data
Deficient have been described recently (within the last ten years). These species were described
either from older material that had been misidentified, or from recent collections made (mostly) in
poorly sampled areas. In many cases, the descriptions are based on only one or a handful of
specimens. Given the (usually) small numbers of type specimens and the fact that the type series of
these species are typically obtained from only a single locality, adequate information on the biology
and distribution of these species for an accurate assessment is lacking.
Of the remaining species assessed as Data Deficient, three of them (Anabas cobojius, A. testudineus,
and Gobiopterus chuno) are widely distributed taxa that most likely consist of several
morphologically similar species. Until the taxonomic identities of material from throughout the entire
known distribution can be adequately resolved, it would not be possible to accurately assess the
conservation status of these species because current information on the distribution and biology of
these species is confounded.
The remaining 65 species are assessed as Data Deficient primarily due to the uncertainty surrounding
their taxonomic status, or to the paucity of recorded information comprise those that have been very
poorly represented in museum collections worldwide. These are species that are typically only known
from the type series, i.e. they have not been collected since the original description. In some cases,
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the type specimens are no longer extant, making the identification of these species more difficult,
especially if the original description and the accompanying figures (if any) are inadequate. Where
specimens are available, these are usually collected from one or only a handful of localities and
almost always without any information on the biology of the species, making an accurate assessment
of their conservation status impossible at the moment.
Fig. 10
Map showing Data
Deficient species
richness in the eastern
Himalayan region
The high percentage of species assessed as Data Deficient highlight the need for greater
understanding of the freshwater ichthyofauna of the Eastern Himalayas. Given that continued
discoveries of new species of fishes from this area are likely to continue at an accelerated pace, the
disparity between our knowledge of the diversity and the biology threatens to grow wider. This is
especially true for the small-sized species of freshwater fishes (for which we expect a much greater
diversity to exist in the Eastern Himalayas than is currently recognized), which are generally the last
to be discovered in any surveys of freshwater fish fauna (Lundberg et al., 2000). In addition to the
need for resolving the taxonomy of the freshwater ichthyofauna of the region, more quantitative data
on yields and process-oriented investigations are also needed for a better understanding of the
population of fish species in the Eastern Himalayas, as well as to provide ample information for the
sustainable management of the freshwater fishery resources.
Extinct Species
No species has been categorized as extinct. CAMP (1998) reported Osteobrama
belangeriValenciennes, 1844, to be Extinct in the Wild from Manipur. This minor carp is highly
priced for its food value in Manipur. The species is presently known to be distributed in the Irrawaddy
basin in Mynamar only. Hora (1921) reported the species from Manipur valley. Menon (1997)
referred to the species as Loktak fish of Manipur and reported the fish to be disappearing fast due to
the introduction of common carp on the lake.
The species is known to migrate from the Irrawaddy to Manipur valley where they breed and grow.
With the construction of the Ithai barrage across the Manipur river for Loktak hydro-electric project in
the early 1980’s, the route of the species to the valley has been disrupted. The fish, now has been
11
successfully introduced to breed and is cultured in the state. O. belangeri has been declared as the
‘State Fish of Manipur’ by the government.
12
X.4
Major threats to fishes
The river systems within the Eastern Himalayas include some of the cradles of human civilization. As
such, anthropogenic modification of the riverine ecosystems in the region has been going on for
thousands of years. Given the fact that sustained and pervasive human impacts are typical of the
rivers in the region, accurate assessment of the extent of human impacts on riverine biodiversity is
thus impossible (Dudgeon, 2000). The threats to freshwater biodiversity can be divided into five
major categories (flow modification, habitat degradation, over-exploitation, species invasion and
water pollution; Dudgeon et al., 2006). With the possible exception of species invasion, the other four
threat categories are amply represented in the Eastern Himalayas, and should be regarded as the major
threats to the freshwater ichthyofauna of the region.
The Eastern Himalayas is a region criss-crossed with numerous river systems; given the strong human
presence in this region, flow modification schemes such as dams and canals have a ubiquitous
presence here. Hundreds of multi-purpose reservoirs for water supply, irrigation, hydropower and
fisheries have been constructed, as well as numerous barrages for water diversion (Smakhtin &
Anputhas, 2006). Such alterations of natural flow regimes have a negative effect on the freshwater
ichthyofauna of the region, such as the obstruction of fish breeding migrations (Dudgeon, 2005).
Some of these dams (e.g. the Farakka barrage in the Ganges River) have been around for some time,
but and their negative impact on the fish populations has been documented, particularly for fish
species undertaking spawning migrations such as Tenualosa ilisha (briefly reviewed in Rahman,
2006). Although an ecological catastrophe was narrowly averted with the cancellation of the InterLinking of Rivers Plan (a massive project that envisaged the linking of many of the major river
drainages in India to divert water from the Ganges-Brahmaputra system to the drier areas in the
southern and western parts of the country), flow modification of the river systems in the Eastern
Himalayas has become an irrevocable part of the landscape (given the pressing need for water
resources in the region) and the termination of this scheme is likely to be only a temporary respite.
In addition to flow modification, the freshwater ichthyofauna of the region is also threatened by
habitat degradation. Many floodplains have been cut out from rivers by embankments and remaining
riparian lands are under intensive agriculture and grazing pressure. Human settlements, deforestation,
mining and other activities have also degraded the river catchments and increased sediment loads of
all rivers (Smakhtin & Anputhas, 2006). Although the effects of increased turbidity on fishes in
general are well documented (Bruton, 1985), very little is known about its direct impacts on the
freshwater ichthyofauna of the Eastern Himalayas.
The over-exploitation of fishes, chiefly for food, is a major concern within the Eastern Himalayas.
Overfishing in inland fisheries can have severe consequences, not only for freshwater ecosystems, but
also for the human inhabitants of the area (Allen et al., 2005). Given that the area encompasses some
of the most densely inhabited areas of the Indian subcontinent, the pressure to fish populations from
capture fisheries is undoubtedly very high. The fact that the inland fisheries in the Indian
subcontinent are largely unregulated is a major cause for concern. Another major obstacle to the
sustainable management of the freshwater fisheries resources is the paucity of empirical data
regarding levels of exploitation and their effects on the fish populations. What little available data
paints a sobering picture, with steep declines in catches of common food fish species over the last few
decades strongly implying that current levels of exploitation are clearly unsustainable (Patra et al.,
2005; Mishra et al., 2009).
The impacts of alien invasive fish species on the freshwater ichthyofauna of the Eastern Himalayas
has received little attention. There have been few published inventories mapping the distributions of
13
the invasive species. Although they have been listed in more general faunistic works of the region
(e.g. Vishwanath et al., 2007), the few studies on invasive fishes available (e.g. Bhakta &
Bandyopadhyay, 2007) are frequently very geographically circumscribed. It is indicative of the state
of research on alien invasive fishes of the region that the highly invasive loricariid catfish
Pterygoplichthys has only been reported from the Eastern Himalayas relatively recently (Hossain et
al., 2008; Sinha et al., 2010), despite the fact that it has most likely been introduced to the region
much earlier. In a similar vein, the negative impact of the alien invasive common carp (Cyprinus
carpio) on native cyprinids in the Ganges River drainage has only recently been documented (Singh
& Lakra, 2006; Singh et al., 2010) even though this species is likely to have been established decades
ago (having been introduced in India as an aquaculture species about 50 years ago). This mirrors the
situation in southern India, where the potential impacts of alien invasive fishes on the native
freshwater ichthyofauna are only beginning to be studied in greater detail (e.g. Khan & Panikkar,
2009; Knight, 2010). We can thus consider the state of our knowledge on invasive fish species and
their impacts on the native ichthyofauna in the Eastern Himalayas to be early in the learning curve.
The major rivers in the eastern Himalayas, particularly the Ganges River, suffer from considerable
pollution as a consequence of the high human density in the region. Untreated sewage, industrial
effluents, pesticeds and partially cremated human bodies are routinely discharged into the Ganges
River (Ajmal et al., 1984; Ahmad et al., 1996; Pimental et al., 1999). The effects of pollution in the
major river systems of the Eastern Himalayas have been well documented (Gopal & Agarwal, 2003),
and include massive fish mortalities.
Manipur valley
Threats of the Manipur valley along with those of Loktak Lake are discussed here. Hora (1921)
reported that unlike Inle Lake of Myanmar, fish species in the lake are not specialised and endemic.
They are also found in the nearby streams of the valley. Manipur valley was very rich in its native
species. Hora (1921) listed 56 species from the state and described six new species. Many species
listed from the Loktak lake is not found there now. In 1980’s state government started introduction of
Indian major carps and Chinese carps for culture. Millions of the seeds have been released in the lake.
Major catch from the lake by an indigenous encircling type of fishing ‘phoom namba’ was
Osteobrama belangeri and Wallago attu. Menon (1989) wrote that O. belangeri, the Loktak fish was
nearing extinction due to the introduction of Common carp. Crossocheilus burmanicus Hora, 1936,
Syncrossus berdmorei Blyth, 1860, Bangana sp. Ompok bimaculatus (Bloch, 1794), Puntius
conchonius (Hamilton, 1822), Eutropichthys, Clarias, Labeo pangusia (Hamilton, 1822), the common
catches from the lake as well as from the valley area are missing. Grass carp, common carp,
Notopterus notopterus, Tilapia are the common catches from the lake now. Clarias gariepinus is even
found in the lake now.
Construction of Ithai barrage is one factor which disrupted migration of fishes from the Imphal river.
Loktak in fact has become a reservoir facilitating spread of Indian major carps and exotic carps.
Native species have lost their spawning habitats. Besides the above mentioned species, C.
burmanicus,
Synchrossus
berdmori Raiamas guttatus of
Kharung pat and other
nemacheilines which were
widely found in swamps,
streams and irrigation canals
are now no more seen in their
habitat. Tombi Singh &
14
Shyamananda (1994) reported that the Loktak lake ecosystem had changed considerably since the
commissioning of the Lokatak multipurpose project. The natural wetland with fluctuating water level
had been converted into a reservoir with almost constant water level thereby bringing about basic
hydrological changes and resulting in several problems for lake biota.
Clarias magur has been categorized as endangered species. The species was caught in plenty in the
past when the water levels in paddy fields receeded. Flooded paddy fields and nearly trenches were
the habitat for the fish. These fishes were smoked and stored for consumption in the offseason. The
species has the habit of nest building for parental care. Nests in the form of pits in the mud are
constructed by the fish. However, the fish is very rare now. The increasing use of pesticides at high
doses in farming probably is a cause of the decline of the population of Clarias. On the other hand,
there could be competition for survival with the invasive species, C. gariepinus.
During heavy rainfall and floods, there has been siltation of the water bodies due to destruction of
river embankments and soil erosion. Some of the present agricultural fields in Manipur were once
wetlands with capture fishery resources.
Fig. 11. Loktak lake
Most of the rivers in the plain are small and become very lean in winter. Available water is used for
irrigation and water supply. In the hills, all the rivers and streams are rain fed. Many streams dry up in
winter.
Sand and pebble mining is done widely for construction works. As a result, populations of species
such as Lepidocephalichthys guntea, L. berdmori, L. irrorata, Pangio pangia have drastically
declined.
The text in the box may be elaborated by assessors and evaluators who have better knowledge
about the conditions in Assam and adjoining areas.
The Brahmaputra
The mighty river, about 2,900 km long, originating in Tibet and traversing across China, Arunachal
Pradesh and Assam in India and Bangladesh supports nearly 200 species of aquatic vertebrates,
almost exclusively fishes. This faunal composition includes not only a wide variety of food-fishes but
also about 50 varieties of aquarium fishes. The Brahmaputra which drain the North-East India
contains almost 30% of countries total Water Resources.
There are 12 large and 7 small dams under construction in north east India (across the Brahmaputra
and the Barak) which would generate about 3000 MW of power. However, proposals for massive
plans of generating 55,000 MW power by setting up around 100 projects in the highly seismic region
could inflict irreparable damage on forest cover, induce floods, displace people (Assam Tribune,
January 25, 2010) and even lead to earthquake.
Floating restaurants on the river Brahmaputra in the vicinity of Guwahati city has caused concerns.
Hardly any river fronts are visible now. Leftovers and plastic bags are easily dumped into the river
causing threat to aquatic life and causing environmental pollution (NDTV).
Excessive deforestation, destructive fishing using dynamites and poisons are additional threats to
aquatic biodiversity in the northeastern states of India. Sidetracking and drying up of parts of hill
streams for fishing are also practiced causing threat to species endemic to such habitats.
Chinese hydropower lobbyists are calling for construction of the world's biggest hydro-electric
project on the great bend of the Yarlung Tsangpo – the Tibetan name of the river which could
generate about 38 gigawatt of power on the upper reaches of the Brahmaputra river as part of a
15
huge expansion of renewable power in the Himalayas. The proposal has caused concerns of
downstream nations, India and Bangladesh, which access water and power from the river.
Extirpated species
Ministry of Agriculture, Government of India (1997) wrote to all states and union territories of India
to destroy all the stocks of exotic magur (Clarias gariepinus) and bighead (Hypopthalmichthys
nobilis) which have been introduced into the country without official sanctions. The government did
not want the fishes to establish in the natural environment and cross with the endemic species.
However, the fishes are available in the markets still now. The government need to be more serious
about the conservation of aquatic environment.
IMAGES OF FISHES MAY BE INSERTED IF REQUIRED
Amblyceps arunachalensis
Badis tuivaiei
Puntius manipurensis
Schistura kanjupkhulensis
Psilorhynchus microphthalmus
16
Semiplotus semiplotus
Semiplotus modestus
17
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