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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 1 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 4 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 5 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 6 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 7 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. 8 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, 10 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 References Abell, R., Thieme, M.L., Revenga, C., Bryer, M., Kottelat, M., Bogutskaya, N., Coad, B., Mandrak, N., Balderas, S.C., Bussing, W., Stiassny, M.L.J., Skelton, P., Allen, G.R., Unmack, P., Naseka, A., Ng, R., Sindorf, N., Robertson, J.,. Armijo, E., Higgins, J.V., Heibel, T.J., Wikramanayake, E., Olson, D., López, H.L., Reis, R.E., Lundberg, J.G., Sabaj Pérez, M.H. and Petry, P. 2008. Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation. 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