A Review of the Ganges Basin: Its Fish and Fisheries - A.I. Payne¹ R. Sinha² H.R. Singh³ S. Huq⁴

¹ Imperial College, University of London, UK

² University of Patna, Bihar State, India

³ University of Allahabad, Uttar Pradesh, India

⁴ International Institute for Environment and Development (IIED), London, UK

All correspondence to: Dr A.I. Payne, Imperial College, 47 Prince’s Gate, London SW7 2QAUK E-mail: [email protected]

ABSTRACT

The Ganges Basin drains an area of 814 800 km², spans the countries India, Nepal and Bangladesh and is occupied by around 200 million people. In its lower sectors it contains some of the highest population densities in the world and also includes major urban areas. There is pollution from industrial and domestic sources. There is also an intense demand for water principally for agriculture. In India all tributaries of the Ganges are controlled by barrages, which divert an estimated 66 percent of the flow for large-scale irrigation. Water is returned with reduced quality and increased chemical contamination. The barrages form barriers across the river. The largest is the Farraka Barrage, which diverts most of the flow down the Hooghly Canal and has been the source of considerable political disagreement between India and Bangladesh, although a Water Sharing Agreement was reached in 1995. The upland cold-water zone in Nepal and northern India has a diverse fish community characterised by migratory and specialised torrent species. This region is thought to have suffered from the effects of erosion from excessive forest clearance. The fish zone extends up to some 1 680 m altitude although fishing probably does not extend above 1 200 m. Fishing yields are comparable to lowland African rivers of the same order. The upland rivers support a significant fishery, which provides an unseen contribution to the welfare of the rural mountain population. The fishery across the whole of the lowland basin is driven by demand from Calcutta and Bengal where fish eating predominates. The proportion of major carps in the fishery declined from 43.5 percent to 29 percent by 1972-76 and 13 percent today. The reduction in dominant species may explain the success of enhancement programmes in several parts of the basin. The anadromous hilsa has also declined due to the Farrakah Barrage and the inaccessibility of the connecting canal. Significant reductions in catches of around 1 600 tonnes or 13 percent over 10 years were found at Allahabad and on the Ganges (Padma) in Bangladesh. Subsequent analysis shows that most of the reduction was due to reduction in rainfall and that there was a close correlation between catches and river discharge or rainfall. Clearly, any basin activity which affects discharge will impact on many aspects of river usage. India has been pursuing the Ganga Action Plan to help control pollution and conserve biodiversity. Bangladesh has a National Water Management Plan and National Environmental Management Plan with aims to integrate water availability amongst multiple uses and generally to regulate water quality and conserve biodiversity. In addition to national regulatory environments, there are also annual tri-partite discussions between the states of the basin to increase international regulation. All of these policies and actions contribute to the long-term status and prospects of the basin.

INTRODUCTION

The basin is located 70-88°30’ east and 22°-31° north (Figure 1). The total drainage area exceeds 1 060 000 km² and the basin is the fifth largest in the world (Welcomme 1983). The length of the main channel from the traditional source of the Gangotri Glacier in India is some 2 550 km. The course of the river is characterised by steep torrential upper reaches and extensive, meandering lower courses. The catchment area encompasses India (80.1 percent of the total basin area), Nepal/Tibet (19.3 percent basin area) and Bangladesh (0.6 percent basin area). Virtually, all of the Nepal Himalayas are included in the catchment area and the basin occupies 25 percent of the land area of India. Altitude within the basin ranges from 8 848 meters above sea level (masl), the peak of the high Himalayas, to sea level in the coastal deltas of India and Bangladesh.

Figure 1. Ganges River Basin (from Cumming 1993)

Vast amounts of sediment are transported downstream by the river and distributed across the fringing floodplains during the period of inundation. Ultimately, a large proportion of the sediment is transported beyond the coastal delta and into the Bay of Bengal. Estimates of the quantity of topsoil transported through the main channel are of the order of 240 million m³ yr^-1 (CPCB 1984). The waters of the Ganges carry one of the highest sediment loads of any river, with a main annual total of 1 625.6 x 10⁶ tonnes compared to, for example, 406.4 x 10⁶ tonnes for the Amazon.

The annual volume of water discharged by the Ganges is the fifth highest in the world, with a mean discharge rate of 18.7 x 10³ m³ sec^-1 (Welcomme 1985). Within the catchment area there exists extreme variations in flow, both spatial and seasonal, to the extent that the mean maximum flow is 52.3 times greater than the mean minimum flow (Welcomme 1985). Estimates of the maximum extent of land prone to flooding throughout the basin vary considerably but are of the order of 295 km² in India and 77 000 - 93 000 km² in Bangladesh, although the latter value is the combined flooded area due to the confluence of the Ganges, Brahmaputra and Meghna, in that country. The flood regime varies along the course of the river and rainfall values differ locally but the predominant pattern is for a low flow dry season from January to May and a wet season from July to November, with a peak flow usually in August (CPCB 1984). The flood season is more protracted in the lower sections of the river. The main sources of water in the basin are direct seasonal rainfall, mainly from the south west and glacial and snowmelt during the summer. There is some debate as to the relative roles of precipitation in the upstream catchment area or local rains in the annual flooding patterns (Chapman 1995). The main channel of the Ganges carries a lot of sediment that makes it very turbid. In the upland regions, however, some of the inflowing streams and tributaries are exceptionally clear. Those that are clear are spring fed, whilst those which are turbid with a high sediment load, are snow fed. Spring fed streams come from clean underground sources, usually at moderate or lower altitudes. The snow fed streams result from the melting of snow and glaciers from the heights of the Himalayas, which wash down heavy loads of sediments from the underlying moraines. The sediment is generally pale grey in colour and can be very heavy. In this respect, the waters of the upper Ganges closely resemble those of the Solimoes, the main stem of the Amazon. The water of the Solimoes has been classified as a “white water” by Sioli (1964), typified by a heavy pale sediment load, an alkaline pH and relatively high total dissolved solids. This has been attributed to the effects of erosion by snowmelt on young, relatively un-weathered mountains, which in the case of the Amazon derives from the Andes. All of these characteristics are shared with the Ganges which can be regarded similarly as a “white water” derived from the Himalayas which are themselves geologically young and un-weathered. There is considerable concern in the upland regions, particularly in Nepal, that deforestation and degrading land practices are leading to increased erosion with higher sediment loads and changed flooding patterns within the river. Given the nature of the river and the lack of quantitative data this has been difficult to confirm.

The main channel of the Ganges begins at the confluence of the tributary rivers, Bhagirathi and Alaknanda, which descend steeply from the upper Himalayas, at Devprayag some 520 masl (Table 1). This then cuts through steep gorges to emerge into the Gangetic plain at Hardwar. Hereafter, the river meanders eastwards for 2 290 km across the plain to Farakka, close to the border with Bangladesh. Just downstream of Farraka the main channel divides into two branches, the Bhagirathi which flows south to the Hooghly and Calcutta and the Padma, which flows into Bangladesh. Both feed a number of distributaries to form one large delta and floodplain, which includes the Sundarbans mangrove area.

The main channel receives a number of major tributaries. The northern tributaries that enter on the left bank after descending from the Himalayas in Nepal, principally the Karnali (Ghaghara), the Buri Gandak, Gandak and Kosi Rivers. There are also southern tributaries, principally the Yamuna, Son, Chambral and Damodar. The northern tributaries provide around 60 percent of the water within the basin.

The Ganges Basin provides, therefore, geographically and environmentally very diverse features that are reflected in its resources. It is also politically diverse since it is shared by three countries and, moreover, is one of the most populous places on earth. Around 450 million people live in the basin, at an average density of over 550 km^-2, which in certain localities and particularly in the delta, rises over 900 km^-2. There is, consequently, a considerable demand and competition for resources, particularly the water itself. Most of the tributaries are controlled by irrigation barrages and there are two major barrages across the main channel, one at Hardwar which abstracts much of the water at this point to irrigate the doab region and one at Farakka which diverts water down to Calcutta and which has been the source of much dispute between India and Bangladesh. All of these structures modify the flow of the river and may considerably influence fish distribution. Further impacts are felt on the fertile floodplains where empolderment for rice farming is practised, to the extent that some 40 percent of the floodplains of Bangladesh have been modified. Fish and fisheries are both an important resource and activity in their own right but also provide indicators of the overall impact of anthropogenic changes over the basin. The numbers of people and also the extent of industrialisation further mean that both domestic and industrial pollution will affect the aquatic environment. This also emphasises the need for a unified approach to management of the basin and it is for this reason that the name of Ganges is used here although it is known locally as Ganga in India and Padma in Bangladesh.

The literature on the Ganges is rather fragmented and tends to reflect work done on a national basis. To provide a basin-wide approach, this has been brought together (Temple and Payne, 1995) as a starting point. In addition to referring to national literature, the present review also draws upon a survey carried out into environmental, fisheries and socio-economic factors along the Ganges valley, from the upper reaches in Nepal to the delta in Bangladesh, which has been requested elsewhere (Payne and Temple 1996). The river can be segregated into a number of physical sections for purposes of discussion:

• Upland reaches - source at 4 100 masl, 25 km to Rishikesh (Figure 1) at 360 masl, includes union of Bhagirathi and Alaknanda Rivers at Devprayag (510 masl) gradient 1:67.

• Equivalent range in northern tributaries to point where they enter the Gangetic plain.

• Upper plains - Rishikesh to Allahabad (58 km masl) with main intersection with plain at Hardwar (310 masl) with mean gradient 1:4100.

• Middle plains - Allahabad to Farakka through the lowlands of Uttar Pradesh, Bihar and West Bengal, with fringing floodplains. Includes the large flood-able area of the Bihar Wetlands where the Kosi joins the main river.

• Lower plains - the delta in Bangladesh and India, which includes the Sundarbans and an extensive floodplain.

PHYSICO-CHEMICAL CONDITIONS

In general terms, the Ganges water is alkaline with a pH above 8 and a conductivity of 160-410 µs (Table 1). The alkaline pH reflects underlying soluble calcerous rocks in parts of the catchment area. The conductivity, which increases along the length, is relatively high. Most tropical rivers have a conductivity less than 400 µs, but many in Africa and South America, including the Amazon and the Congo, for example, have conductivities less than 150 µs (Welcomme 1985). This is a function of the relative youth of the mountains in the catchment area and the sedimentary nature of some of the underlying parent material. The northern tributaries have similar characteristics.

Table 1: Hydrologiccal data for various sites along the Ganges basin by altitude

Temperature shows considerable downstream variation and is probably a major environmental factor influencing the distribution and nature of fish communities (Table 1).

Seasonal variation in temperature is quite marked. In the upland sector (580 masl) temperatures range from 16.5-18.7°C for October to May respectively. At the major transitional zone of Rishikesh/Hardwar the recorded range was 20.8-20.4°C between the same periods. The upland tributary of the Son Kosi showed a range of 15-20.6°C over the similar period.

Once on the plains the rivers warm up rapidly, for example, temperatures can be up to 4°C higher only 30 km below the transitional zone of upland to plains. Downstream at Allahabad, seasonal temperature ranges can be from 15.1-29.1°C or at Patna in Bihar 18.6-33°C. Equally, in the southern tributary of the Yamuna the average seasonal range is 14.9-29.1°C.

There does, therefore, appear to be two rather different temperature regimes between upland and lowland sectors, with a relatively well-marked transitional point between them. The main upland snow-fed rivers do not reach more than 21°C, which is the highest recorded temperature at the transitional point on the river. This is the point at which there is also a major change in the physical nature of the river from erosional to depositional zones, i.e. rocks to sand and also where the cold-water fish communities cease to be found. It is also where the river changes from being torrential, turbulent and running through steep gorges to a wider, deep river running between sand banks, often with a fringing floodplain.

FISH RESOURCES

Aspecies list is provided in Appendix 1.

Surveys in Nepal have shown no fish records beyond an altitude of 1 650 masl (Shrestha 1978) and fisheries have not been noted above 1 800 masl (Jha 1992). In the appended list (Appendix 1) the uppermost point on the main stem of the Ganges is the Alaknanda, 460-1 600 masl (Singh, Badala and Dobriyal 1987) where the fish zone probably ends. Slightly below this is a sample from the upper Ganges in the Garwhal region (460-310 masl) above the transition zone at Rishikesh/Hardwar. The sample for the northern tributary of the Kosi (79-600 masl) takes into account both lowland and upland species for the river as a whole (Khan and Kamal 1980). The results of two-year surveys at Allahabad and Patna are included for the upper and middle plains. A comprehensive survey from the Padma in Bangladesh represents the delta and floodplain (FAP17 1994; ODA1997).

In total for the whole freshwater sector 161 species are recorded. Other species counts have included estuarine species or have been confined to one country of the Basin (e.g. Talwar 1991; Rahwan, 1989). River sectors will vary as to what proportion of these species they contain. Thus the number recorded for the Kosi is 103 or 63 percent of the total. Numbers will also increase as further surveys are done.

The Alaknanda has the lowest number of species for any sector of the river. However, a total of 41 is still appreciable for a single cold, upland river and gives an indication as to how relatively rich the cold upland communities are. The community of the Alaknanda is characterised by a few specialised cyprinid types, specifically the snow trouts Schizothorax/Schizothoraichthys spp, the mahseers (Tor spp) and small Garra spp, together with some of the mountain loaches, Noemacheilus spp and the highly specialised sisorid torrent cat fishes, Glyptothorax spp. (Appendix 1). A typical day’s fishing is likely to produce representatives of each of these groups although the emphasis is always upon the snow trouts and mahseers, with regard to numbers.

The fish community of the upper Ganges is very similar to that of the Alaknanda, although a few lowland species begin to appear, such as Mastacembelus and Channa so that the final species total is a little higher at 54. Again, however, numerically the snow trout and mahseers would tend to dominate the fishery.

The snow trout and mahseers are both migratory and it is essential to understand their movements in order to interpret their role in the fishery. The snow trout, Schizothorax spp, migrates upstream and is reported to spawn in March to June at water temperatures ranging from 14-21°C in the Himachal Pradesh (Negi 1994). It is generally regarded as tolerating waters from 8°C to 22°C. Spent individuals and the presence of fry in October may suggest a longer or later spawning period in the Garhwal Himalaya. For the mahseers, upstream migration takes place at the beginning of the monsoon and they may spawn during the period of July to September (Negi 1994). The common species, Tor putitora (Hamilton), could have three peaks between February and September.

The rivers and few lakes of the Ganges Basin in Nepal contain more than 130 species (Shrestha 1990). The upland waters have a similar cold-water fish community to the upper waters of the main stem of the Ganges and Alaknanda in India. This does not extend into the Terrai, the lowland area of Nepal, beyond the transition zone, where the rivers are wider, warmer and meander more than those of the more torrential upper reaches, in particular the snow melt streams of the Himalayas. The lowland regions have a similar fauna (Smith 1991; Shrestha 1990) to that of the other sections of the lowland Ganges of the plains (Appendix 1).

The lowland sites at Allahabad, Patna and Bangladesh showed considerable similarities with communities dominated by cyprinids, particularly major carp species and catfishes. A distinction can be made between main channel migratory species, such as the major carps and the floodplain resident species that are often small and have accessory respiratory systems and prolific reproduction.

In the delta region of Bangladesh, some from the estuary start to appear such as the scieanid, Scieana coiter, the mullets, Rhinomugil corsula and Sicomugil cascasia. Particularly significant is the anadromous Tenualosa ilisha or ‘hilsa’, which was still recorded as far up river as Allahabad in the 1993 - 1994 survey (Appendix 1).

It is perhaps significant that the highest individual total of species (103) is for the Kosi River, which included both upland and lowland communities (Khan and Kamal 1980). The other northern tributaries are also quite rich in species, with 74 being recorded for the Karnali and 69 for the Mahakali (Shrestha 1990).

FISHERIES IN THE BASIN

COLD WATER UPLAND FISHERIES

The cold-water upland fisheries can be defined as those occurring in waters with temperatures up to 21°C, the limit of the snow trouts. Otherwise, they have been related to the temperature tolerance of introduced salmonids, i.e. 0-20°C (Jhingran 1991). These fisheries are those dependent upon the typical fish communities of the Himalayan sector of the Basin. The approximate boundary in India is at Hardwar (230 masl), as the river leaves the Siwalik range and enters the plains and in Nepal where the northern tributaries enter the Terrai. There may be some overlap of species since the major carps, more typical of the lowland communities, can extend to 250-450 masl in Nepal (Shrestha 1978). There are, for example, tributaries in the mountains, such as the Seti which arise below the snow line and which are relatively warm and in which snow trout seem to occur only seasonally (Payne and Temple 1996).

The mountain fisheries have been very poorly documented. The steep gorges of the Himalayan regions of India and Nepal render fishing a difficult and hazardous operation. The variety of habitats and difficulty of the environments give rise to a variety of fishing techniques (Shrestha 1994). The commonest is the cast net, where the rivers meander and also found here, in both India and Nepal, is a long-line technique which has a series of nylon constricting loops, which act as snares, rather than hooks which is particularly effective for snow trouts. This is variously called the “fase”, “passo” or “gill net”. Originally the snares were made of horsehair and dangled from a rod (Shrestha 1979). In addition to these, the use of dynamite is common and also of electricity by using car batteries or connecting with insulated wires to overhead power lines. Traps are also common in some places.

There are reported to be very few professional fishers in the upland region but a widespread general participation in fishing activity. In the Kuman Himalayas of Uttar Pradesh, snow trout are estimated to provide 20-80 percent of the catch, with mahseers contributing 20-27 percent (Bhatt and Pathak 1992). There appear to be two peaks in the catch of snow trout; the first in June/July during the rising waters of the early rains and the second in September/October as the river waters begin to fall. The minimum catch rates are generally through the winter season. For mahseer, the peak landings occur during May/June and this coincides with upstream movement for spawning. It is considered that in the Himalayan reaches, the catches are related more directly to water temperature than to altitude (Bhatt and Pathak 1992). Both snow trout and mahseer may migrate downstream during cold spells, which inevitably leads to decline in the upstream landing.

Distribution of mountain fisheries in the Indian Basin is necessarily patchy owing to the steep inaccessible gorges through which the river runs in this region. In addition, however, the extreme sanctity of certain points on this river, which is central to the Hindu faith, means that fishing is often forbidden in such places. Examples of such points are the towns of Hardwar and Rishikesh where the River Ganges first meets the plains and Devprayag where the two main upstream branches unite. Here, vegetarianism is expected and fishing is totally prohibited on religious grounds. Similarly, much of the main channel from the plains up to its source is a route of pilgrimage where the consumption of flesh, fish or fowl is not encouraged. Markets are, therefore, very limited.

A catch survey has been carried out on the Bhagirathi River, a headwater feeder tributary in the Garhwal Himalayas (Sharma 1984; Sharma 1988), close to the site of the Tehri Dam. Eight different methods of fishing were documented and 23 species of fish recorded. The most common were the snow trouts, Schizothorax (3 species) contributing between 61 and 74 percent of the catch over a year. The sites ranged from 1 855 masl to Tehri at 770 masl with seasonal temperatures kept between 10.2 and 19.4°C by snowmelt near the source.

Surveys along a number of stretches of upland rivers in India and Nepal showed significant fishing activity along most of them (Payne and Temple 1996). Estimates of catches at four points along the Alaknanda in the Garhwal Himalaya showed a range of between 1 035 to 2 475 kg km^-1 year^-1 with an average around 1 650 kg km^-1 year^-1. Alower tributary, the Nayer, produced 621 kg km^-1 year^-1 whilst a tributary of the Bahgirathi yielded 2 250 kg km^-1. This last estimate reflects a genuine abundance of fish and not just fishers and markets. These, however, migrate in for a short period of the year in the pre-monsoon, March to June, to give a peak in fishing rather later than at most sites where fishing takes place throughout the low-water season, from October to March. This may indicate that the tributary is in an upper reach spawning area.

In Nepal, surveys have been carried out in the Seti, Trisuli, Narayani and Rapti Rivers of the Gandaki Basin and Sun Kosi and Indrawati Rivers of the Kosi Basin. All showed varied significant activity usually by part-time or occasional fishers for home consumption or a little extra money but some professional fishers had recently migrated in from the Terrai and India, even as far away as Bombay, to escape competition elsewhere. An estimate of catch rates of the Seti River (270 masl) gave 1 490 kg km^-1 year^-1 composed of a mixture of warm and cold-water species.

In considering the cold-water upland areas of the Ganges Basin, an average estimate of some 1.5 tonnes km^-1 for annual fish production is indicated. The limits of the cold-water area can be defined at its lowest limit by this distinction of snow trout at around 180 masl but more realistically by the temperature less than 21°C throughout the year. The upper altitudinal limit is unlikely to extend much beyond 1 600 masl since most species of commercial importance do not extend up the rivers of the Himalaya much beyond this (Shrestha 1978). At such altitudes the opportunities for fishing are also scarce and difficult. The upper limit for significant fishing activity may well be 1 200 m or less.

Welcomme (1974) found the catch rates for African rivers to fall mainly within 1-15 tonnes km^-1 year^-1. However, catch rates increased significantly downstream. Thus, for example, a river around 100 km from its source would yield in the order of 1 tonnes km^-1 year^-1. The upland rivers surveyed in the Ganges Basin are this order of difference from the source and their yields are comparable. Since there are a number of dams for hydropower projects under planning in this region, such order of magnitude estimates are useful to enable a value to be put on the fish resources.

WARM WATER LOWLAND FISHERIES

The fisheries from Hardwar to West Begal are rather different in nature to those of the upland Himalayan region both with regard to the species taken and fishing activities.

Surveys were initially conducted in 1957 by the Central Inland Capture Fisheries Research Institute, Barrackpore, (CIFRI) and regular updating of data between 1957 and 1981-82 showed no indications of any significant changes in fishing intensity in the middle reaches of the main channel and lower sections of the Yamuna (Natarajan 1989). The implication was, therefore, that any observed changes in catch rates found during coincidental fisheries surveys, represented changes in abundance of fish stocks concerned. However, a subsequent report of CIFRI (Jhingran 1991) indicated a perceptible rise in the occurrence of fishing villages, number of fishers and diversity of gears by the mid-eighties. There are 22 fish marketing centres on this stretch of the River Ganges, of which 5 are major and there are 4 centres on the Yamuna. The marketable surplus of fish for each part of the river is brought to these centres, which provided the focal point of the 22-year catch survey sequence carried out by CIFRI (Natarajan 1989).

Fishers can be categorised as “professional”, “part-time” or otherwise. It is clear, however, that true professional fishers fall into a well-defined social category of sub-castes. This often renders their fishing villages distinctive and identifiable. There are no indications, however, of the extent of part-time or occasional fishing among essentially non-fishing groups, which is often a feature of floodplain fisheries elsewhere, including Bangladesh.

As with the upland areas of the Indian sector of the River Ganges, the religious influence on dietary habits along the river itself implies that local markets are unevenly distributed throughout the basin. The major market within the basin is West Bengal in general and Calcutta in particular. The Bengali people of India (West Bengal) and Bangladesh (East Bengal) have a long tradition of eating fish and almost certainly create much of the demand throughout the lowland area of the basin. There are instances of catches on the western rim of the basin in Rajasthan being transported more than 1 500 km by train to Calcutta to reach a suitable market.

The main gear types used in the lowland areas are seine or dragnets, gill nets, scoop nets, cast nets, long lines and traps. However, within these broad categories are a diversity of types and sizes (Bilgrami and Datta Munshi 1985), which are often designed to catch a particular range of fish species.

Most fishery surveys so far conducted on the River Ganges, both in the Yamuna and the main channel have been based upon selected landing centres (Jhingran 1991). The earliest surveys, between 1958-59 and 1965-66, were based on totals of daily arrivals of fish for the Yamuna at centres at Agra and Allahabad and for the main Ganges channel at centres downstream at (west to east) Kanpur, Varanasi, Buxar, Ballia, Patna and Bhagalpur.

During this period, the migratory hilsa formed a major component of the catch from the middle and lower reaches of the main river, contributing 25-39 percent of the total catch between Varanasi and Ballia, just above Patna in Bihar. Hilsa was recorded as far upstream as Allahabad at the junction of the Yamuna River with the main channel, some 900 km from the Hooghly estuary and the Indian Ocean, but hilsa is rarely found penetrating upstream of the River Ganges as far as Kanpur, or upstream of the Yamuna as far as Agra.

In the middle reaches of the Ganges at this time, the most important single group were the major carps (catla, mrigal, rui and calbasu). Together they constituted 53 percent of the catch at Agra, 45 percent at Kanpur and 38 percent at Allahabad, but declined somewhat towards the lower reaches, where they generally accounted for 19-26 percent at Patna and beyond (Table 2). Amongst the major carps, mrigal (Cirrhinus mrigala) tended to predominate in the upper stations, with catla contributing a much smaller proportion. This proportion appeared to become more equal downstream. Since the 1958-66 period L. calbasu has become the commonest of the major carps around Allahabad rather than C. mrigala.

Table 2: Changes in catch composition downstream from Allahabad between 1958 and 1994

Key:

+ from Jhingran (1991)
* from Payne and Temple (1996)
from DOF (1991)
from FAP17 (1994), based on survey, not on catch data
^x - was 37-39% upstream at Ballia and Buxar

The total catches from each landing centre do not appear to show any consistent trends. It is possible that they vary with environmental and hydrological factors. There do, however, appear to be reduced catches of major carps and hilsa over time, particularly at Patna (Table 2). Estimates of catches in the original 1957 survey estimated total annual catches from the rivers Yamuna and the Ganges stretch from Allahabad to Farakka at 770 tonnes and 275 tonnes respectively, which gave a consistent relative yield of 0.75 tonnes km^-1 and 0.77 tonnes km^-1 for the two stretches (Natarajan 1989).

Yield from Allahabad has varied between 5.1-10.6 kg ha^-1 and at Bhagalpur between 16.8 and 26.3 kg ha^-1 and they show no apparent trend. Yield at Buxar does appear to have declined from 23.1 kg ha^-1 in 1958-62 to 4.5 kg ha^-1 by 1981-84. These yields are low compared to values achieved in the true floodplains of Bangladesh where values of 80-160 kg ha^-1 have been recorded. They are also low on a worldwide scale where yield might typically fall between 40 and 80 kg ha^-1. These values for the River Ganges are, however, obtained solely from the commercial fishery and take no account of the subsistence fishery, although fish is not a favoured part of the diet in this region.

In addition to the fisheries of the main channel, there are also those of the northern tributaries, in particular the rivers Gandak, Buhri Gandak and the Sapta Kosi. All of these rivers meander through the alluvial plains in northern Bihar and, during the monsoons often produce large floodwater areas known as the North Bihar Wetlands. Extensive fishing takes place in these floodplains but this is not well documented (Ahmed and Singh 1990; Ahmed and Singh 1991). In 1965-66 the oxbow lakes of the Burhi Gandak sub-basin alone covered an area of 36 000 ha which provided a fishery of 2 900 tonnes yr^-1 (Natarajan 1989). The natural flow of many of the Northern tributaries such as Kosi, Gandak, Rapti and Sarju, has, however, been affected by a number of hydraulic engineering schemes. For example, the construction of canals for water diversion and flood control along flood prone low-lying areas. It is reported that such schemes have greatly restricted access to breeding grounds for major carps and other species (Natarajan 1989), not to mention the Gangetic dolphin, Platanista gangetica (Smith 1991). Canal projects for water diversion and flood control schemes are regarded as factors largely responsible for diminished production. Nevertheless, these floodplains remain extensive and require assessment. In recent years, stock enhancement by the release of hatchery-reared fingerlings has been attempted. This fishery was reported to be widespread and to be jeopardising the natural recruitment of stock.

Further downstream the river spills out into the delta, which is characterised with a large floodplain and interaction with the estuarine zone. The floodplain is most extensive in Bangladesh and production from the rivers and their associated floodplains varied from 460 000 tonnes in 1983-84 to 561 824 tonnes in 1996-97 (DOF 1998). The largest single component of the inland fisheries in general is hilsa, which migrates up river from the estuary and the Bay of Bengal to spawn. It constitutes around 13 percent of all inland fisheries and 42 percent of river catches. Total riverine catches have been declining from 90 000 tonnes in 1983-84 to 84 463 tonnes in 1988-89 (DOF 1991) although there has been something of a resurgence to around 60 000 tonnes since 1996. Of this riverine total in Bangladesh, the Ganges (Padma) contributes around 4-5 percent but apparent declines have been even more marked, from 12 095 tonnes to 1 641 tonnes over the same period, but again with something of a resurgence after 1995 (Table 3).

The other constituents of the catch are categorised as major carps, catfishes, live fish (any other species with accessory respiratory organs) shrimp and miscellaneous species (DOF 1982 et seq.). The last tends to be the largest, containing as it does, largely small, floodplain dwelling species. The major carps generally provide a small percentage of the catch, being between 3-5 percent for all rivers but only 0.2-2.5 percent for the Ganges (Padma), tiny even compared to upstream areas such as Patna in India. If floodplain catches are included in Bangladesh, along with those from rivers, the major carps may constitute 6-10 percent.