|Freshwater||931||72||No||748||Kottelat, M. and T. Whitten, 1996|
|Conservation||There has been a major recent publication on freshwater fishes in India (Talwar and Jhingran (1992; Ref. 4832, 4833), which after some corrections, contains 748 valid species (Ref. 12217). Recent work indicates that the Indian fish fauna is underestimated and many widespread species are actually assemblages of strikingly distinct species (Ref. 12217). Information on the conservation status of fish species is lacking. Indian rivers, in particular the Ganges, have suffered from a range of human-related activities. These have included large-scale water abstraction for irrigation, construction of dams and barrages, siltation, soil erosion due to deforestation in the catchment areas industrial, agricultural and municipal sources. There has been a steady decline in the total fish and spawn yield of the major carps and the anadromous hilsa, @Hilsa ilisha@. The hilsa was plentiful until 1972 at all centers above the Farakka Barrage in the lower Ganges but catches have reached an all-time low due to the obstruction of its upstream migration created by the barrage. Large dams are becoming a characteristic component of river basins. A number of man-made lakes have been constructed on different Indian river basins for the purposes of irrigation, power generation, flood control and industrial uses. By their sheer size, these lakes constitute an important fisheries resource, but dams radically alter river hydrology both upstream and downstream creating a new artificial aquatic environment with consequent changes in species composition. Oxbow lakes are biologically sensitive areas associated mainly with the rivers Ganges and Brahmaputra. They often act as sanctuaries for commercially and biologically important fish species. Flood protection embankments across the inflow and outflow channels of several such lakes have seriously restricted the lateral expansion of water and consequent ingress of breeding species. Higher rates of water abstraction coupled with siltation in river beds, has led to isolation of oxbow lakes endangering the populations within. Freshwater sites of exceptional biodiversity interest are streams in Kerala and northeast India (Assam, Manipur, Nagaland, Meghalaya, Himachal Pradesh, Mizaram, and Tripura), as well as the major floodplains.|
|Geography and Climate||
India can be divided into four main regions: the Himalayas, the northern river-plains region, the Deccan, and the Eastern and Western Ghats.The Himalayas are a mountain system about 161 kilometres to 322 kilometres wide, which extends 2,414 kilometres along the northern and eastern margins of India. The Himalayas are the highest mountain system in the world. Among the outstanding summits wholly or partly within India is K2, or Mount Godwin Austen (8,611 metres), which is second in height only to Mount Everest (8,848 metres) located in neighbouring Nepal. South and parallel to the Himalayas lies the northern river-plains region, a belt of flat, alluvial lowlands about 280 to 408 kilometres in width. The region comprises the major part of the vast plains area watered by the Indus, Ganges, and Brahmaputra rivers. The plains region of India extends from the border with Pakistan to the border with Bangladesh and continues east into Assam, which is connected with the remainder of the republic by a narrow corridor of land near Darjiling.The central and western portions of the Indian plains region are watered by the Ganges and its tributaries, which drain the southern slopes of the Himalayas; the region is known consequently as the Gangetic Plain.
The Assam region is watered by the Brahmaputra River and its affluents, which rise on the northern slopes of the Himalayas. The Brahmaputra crosses into Bangladesh north of the Khasi Hills. The River Indus rises in Tibet, flows west, and crosses into Pakistan.
South of the plains region lies the Deccan, a vast, triangular tableland occupying most of peninsular India. The Deccan is a generally rocky and uneven plateau divided into natural regions by low mountain ranges and deep valleys. Elevations in the plateau region range from about 305 metres to 1,525 metres (about 1,001 feet to 5,004 feet). The Deccan Plateau is bordered on the east and west by the mountain systems known, respectively, as the Eastern Ghats and the Western Ghats.
The Western Ghats, a bold escarpment overlooking the Arabian Sea, have a general elevation of about 915 metres (about 3,002 feet). Between the Eastern Ghats, which average about 460 metres (about 1,509 feet) in elevation, and the Bay of Bengal is a narrow coastal plain, the Coromandel Coast. In the southern interior, near Bangalore, are the Nilgiri Hills.
Within India there are a great diversity of climatic conditions. For example, annual rainfall at sites within India can vary from as little as 15 cm to as much as 1100 cm. There are similar variations in temperature. On the Kerala coast the average temperature is about 27°C with little daily or annual variation. In the northwest plains summer temperatures may reach 47°C while in winter they may fall to 0°C. The major climatic feature common to all areas is the monsoon. The southwest monsoon, from May to September, is the chief season of rainfall for most areas of India. The southwest monsoon sets in over Kerala and Bengal in late May or early June and extends over the rest of India in late June. It continues until late September or early October when it retreats from the northwest.
Ref. Microsoft, 1996
India is endowed with a vast expanse of open inland waters in the form of rivers, canals, estuaries, natural and man-made lakes, backwaters, brackish impoundments and mangroves. In terms of fish production India ranks second to China with a 1990 yield of over 1 million tonnes.
Peninsular India, that is the areas south of the Indus and Ganges basins, is drained by several important rivers. The two northernmost ones , the Narbada (or Narmada) and the Tapti (also spelled Tapi) have their sources in the low mountain ranges south of the Gangetic plain and flow westwards into the Arabian Sea. The other large rivers flow eastwards into the Gulf of Bengal. These are, from north to south: the Brahmani, Mahanadi, Godavari, Kistna or Krishna, Penner and Kaveri (also spelled Kaweri or Cauvery). An important tributary of the latter is the Bhavani or Bowany River. The headwaters of the Mahanadi are close to those of the Narbada River. The Godavari, Kistna, Penner, Kaveri and their main tributaries have their sources in the Western Ghats and traverse the whole Dekkan Plateau. Many short coastal rivers, south of the Tapti, flow from the Western Ghats westwards into the Arabian Sea.
The aquatic fauna of Peninsular India is not homogenous. The most remarkable freshwater fishes live in the Western Ghats, both in western coastal rivers and the upper reaches of the large rivers flowing eastwards, from Bombay southwards to Travancore and to the tip of the peninsula. Many fishes from the Western Ghats are absent from, or have no close relatives in, the Gangetic plain. Their closest relatives, on the contrary, live in the Eastern Himalayas, in the Assam hills and mountain ranges, and even farther east in Indo-China and/or Indonesia. There are a number of genera that occur in Western Ghats that have disjunct global populations.
The fauna of Peninsular India, particularly the Western Ghats, comprises numerous endemic species in various genera. Most southern Indian endemics have restricted ranges and several zoogeographic subdivisions of the peninsula can be recognised. The most significant endemics are confined to the Western Ghats, corresponding mainly to the headwaters of the Kistna, Godavari, and Kaveri Rivers and their tributaries. The faunas of the small coastal rivers flowing westwards include a few peculiar species, being mainly an impoverished derivation of the faunas of the larger eastern rivers.
The Ganges river system with its main tributaries such as the Yamuna, Gomti, Gandak, Kosi, Chambal and Sone have a combined length of 12,500 km. The Brahmaputra system has a length of 4,023 km. The peninsular rivers such as the Mahanadi, Godavari, Krishna and Cauvery have a combined length of 6,437 km. Rivers Narmada and Tapti, and the west-flowing drainages of the Western Ghats have a combined length of 3,380 km. The Ganges river system is the major habitat of four important fish species of the subcontinent, known as the Indian major carps. The Ganges and its tributaries are of key importance from a fisheries point of view. Indian rivers as a whole provide a means of livelihood for many thousands of fisherman.
Ref. Talwar, P.K. and A.G. Jhingran, 1991