The River Ganges is the most important of all Indian rivers. It is being harnessed for several onsite and offsite benefits for various sections of society. Through varied man-induced interventions, over the years, the river system has recorded changes in its ecological functions, especially at some stations of the middle stretch viz., Kanpur, Varanasi and Allahabad. An attempt has been made in the present paper to understand changes with regard to key parameters of water quality, fish species composition and catches in this stretch, covering the highly populated major states of Uttar Pradesh and Bihar. For this purpose, data available over the years and some new data were utilized. These data reveal that siltation over the years has lowered water volumes and depths at various sections in the middle stretch with over 90% of the sediment comprising sand. The water quality in terms of pH remained higher (7.0 to 8.8) at some stations while dissolved oxygen remained lower (4.5 to 5.8 ppm) in comparison to upper and lower river stretches, suggesting progressive eutrophication. Other parameters, especially nutrients, also showed variations, coupled with variability in plankton density and primary productivity in this stretch reflecting changes in ecological functions. These changes coupled with various engineering interventions has resulted in drastic changes in water flows in the main river channel, the cumulative impact is evident in the drop in fish catches from 932 kg km−1 in the 1960s to 382 kg km−1 in the recent past, and the shift in species dominance from Indian major carps to less economic varieties. This has affected the livelihoods of fishers. The general lack of concern and awareness among the river authorities on requirements of river fishery management has been observed to be main reasons for these changes. Possible policy and governance interventions required to restore the river for sustainable fishery have also been suggested in this paper.
The River Ganges is of unique importance ascribed to reasons that are geographical, historical, socio-cultural, and economic, giving it a status of a national river in India (MOEF, 2009). The river has been facing serious threat due to discharge of various pollutants, on account of rapid urbanization and industrialization. This situation is further compounded by the growing water demand of various competing sectors of economy. In the light of high economic stakes of other sectors from the river system, the interests of the fishery sector happen to get neglected. But from the fishery point of view the river system has its own importance; it is the primary source of Indian major carp brood stock and many other species, while sustaining the livelihoods of many fishers inhabiting all along its course. Therefore, the impact of anthropogenic stresses on the fishery in the middle stretch of the River Ganges was investigated.
The middle stretch of River Ganges flows through the states of Uttar Pradesh, and Bihar on its way to drain into the Bay of Bengal (Figure 1). This region of the Indian part of Indo-Gangetic basin is thickly populated and various sections of society harness benefits from this river system. Critical examination of the available data and supplementary information generated on the ecology and fisheries of this river stretch, spread across different stations, will help establish the current status of the system vis-à-vis fisheries and provide inputs to the river authority for developing better management practices for river fishery in future.
The states of Uttar Pradesh and Bihar have a tropical monsoon climate. It is very hot in the summers across the state. Summer season persists from April to August. The daytime temperature remains very high and usually touches around 45°C. Nights are relatively cooler and the temperature drops down to 28°C. Winter is much cooler with day temperature around 24°C with chilly nights when temperature drops as low as 2 to 4°C across the state. The average annual rainfall varies from 105–110 cm. This extreme seasonal variability in ambient temperature has a great influence on fish stocks and species.
The river bed from Kanpur to Patna is mainly sandy with 80–90% sand and a low percentage of silt and clay. However, in the lower stretch from Bhagalpur to Farakka the sand contribution is much lower (54–69%) with a substantial increase in silt and clay content. The study conducted by Srivastava et al. (1994) revealed that the stretch between Kanpur to Patna suffers from severe textural deformity with sediment blanketed by drifting sand from a number of tributaries, viz., Ramganga, Yamuna, Gomti, Ghagra, Gandak and Sone. The river bed sediment has an alkaline pH (7.4–8.2) and is poor in respect of available nutrients (N – 0.53 to 8.0 and P – 0.06 to 2.2 mg 100 g−1) and organic carbon (0.014 to 0.23%). The sandy bed contributes very little to aquatic productivity in terms of nutrients. However, nutrients flow in from surface runoff and the catchments.
The deforestation, extensive agricultural and other developmental activities in the catchment of this stretch have tremendously increased the silt load which is 3850.49 million tonnes per year at Allahabad and 7096.37 at Varanasi during 1995–2000 (Swamee et al., 2003) Such heavy siltation has resulted in severe hydrological changes such as decreases in water depth and volume in the river. As a result many wetlands have become disconnected with the main river channel and some have become too shallow and invaded by aquatic weeds with hardly any open-water zones. Subsequently due to launch of catchment improvement programme by the Government of India some improvement has been observed during 2002–2007 with a decline in silt load (at Allahabad – 1738.55 million tonnes per year; at Varanasi – 3432.39 million tonnes per year).
Levels of some water quality parameters have changed between three time periods at different stations of the middle stretch between Kanpur and Farakka (Table 1). In 1960 when the river system was not much stressed the values for almost all the parameters were within fairly accepted limits of a good environment. The situation began to change post eighties when during 1987–1988 the Kanpur recorded very low value for dissolved oxygen at <2 mg l−1, while Varanasi registered marginally above 2 mg l−1. However, after implementation of river water quality programme by authorities, during the period 2001–2006 the dissolved oxygen values both at Kanpur and Varanasi recorded marked improvement. In the middle stretch, these two stations were highly stressed in comparison to other stations of the stretch. Specific conductivity values during post eighties and even during 2001–2006 remained high at Kanpur, Allahabad and Varanasi in comparison to other stations, indicating variation in the richness of water in the middle stretch. The data also indicates that this middle stretch, due to high density of human population, also receives organic load that is reflected by high levels of chloride ranging between 18.4 to 35 mg l−1 at Kanpur, Allahabad, Varanasi, Patna and Bhagalpur. These data clearly show that despite the water quality initiative taken by the authorities, only a few parameters in some stretches have improved, but overall improvements are still to be achieved. To address the River Ganges in a more holistic manner, the Government of India set up the “National Ganga River Basin Authority” in 2009 to oversee the environmental improvement of this river system (Ministry of Environment Notification, 2009).
Dams and barrages
The changed hydrological conditions can badly hamper fish breeding and recruitment processes in rivers. In the Ganges, blocking of water passage at Farakka has badly affected the migration of anadromous hilsa (Tenualosa ilisha) and its fishery in the upper reaches is almost negligible (De et al., 1994). This has badly impacted the livelihoods of fishers dependent on the hilsa fishery. Other migratory species such as Pangasius pangasius, Pama pama, large prawns, etc. have also lost their place in the fisheries of upstream stretches. Over the years, the creation of numerous dams/barrages on tributaries and the main river has resulted in severe hydrological alterations in Ganges basin. As a result the flow has been regulated, water volume has declined, silt load has tremendously increased, many floodplain wetlands have lost their connection and breeding and nursery grounds have been lost. The cumulative effect of hydrological degradations has resulted in severe fishery declines in the River Ganges and its tributaries (Sinha, Khan and Jha, 1999); (Vass, 1999, 2006).
The plankton population of the River Ganges has been studied through various surveys initiated by CIFRI from time to time and also reported by Pahwa and Mehrotra (1966); Khan et al., (1996); Sinha et al., (1998); Kumar (1999) and CIFRI Annual Report (2008). The middle stretch is reported by above studies and also estimated during this study to have 7 taxa of cyanophyceae, 22 of chlorophyceae, 16 of bacillariophyceae, 3 of xathophyceae, and 1 each of dinophyceae and euglenophyceae among the phytoplankton. Zooplankton are represented by 10 taxa of rotifera, 5 of cladocera, 2 each of copepod, ostracoda and insect, and protozoa with 5 taxa. The present studies indicate that dominant groups among phytoplankton, in this stretch, were represented by Amphora, Asterionella, Cyclotella, Cymbella, Diatoma, Fragilaria, Gomphonema, Gyrosigma, Navicula, Nitzschia, Pleurosigma, Pinnularia, Synedra (bacillariophycaeae); by Actinastrum, Ankistrodesmus, Chlorella, Closterium, Denticula, Desmidium, Eudorina, Hydrodictyon, Mougeotia, Pediastrum, Scenedesmus, Spirogyra (cholorophyceae), and by Anabaena, Lyngbya, Merismopoedia, Microcystis, Nostoc, Oscillatoria, Phormidium (cyanophycaeae). Among zooplankton, copepods, cladocerans, rotifers and protozoans were the major groups recorded. The maximum abundance of plankton in terms of quality and quantity was observed in the stretch between Kanpur and Allahabad. The overall plankton density in the entire middle stretch varied from 24 to 782 l−1; 146 to 3,649 l−1 and 14 to 8049 l−1 during summer, monsoon and winter season. Maximum density was observed in Kanpur stretch (8,049 l−1) during winter season. Of this the contributions of phytoplankton and zooplankton were 7,953 l−1 and 96 l−1, respectively. Among phytoplankton, dominant group was Bacillariophyceae followed by Chlorophyceae and Cyanophyceae.
Pahwa (1979), Sinha et al., (1998), Khan et al., (1996, 1999) and the present investigation have reported significant average seasonal variability in macro-benthic density at different stations in the middle stretch of river system. The data sets on bottom fauna from different centres viz., Kanpur to Patna ranged from 138–1332 u m−2, 266=-2584 m−2, 184–2530 m−2 in summer, monsoon, and winter, respectively. Insects were highest at Kanpur (98.0%) and lowest at Patna (0.6%) while molluscs were dominant at Patna (99.4%) and minimal at Kanpur. Among insect population dipteran larvae contributed most at Kanpur and Allahabad while at Varanasi trichoptera dominated the benthic population. At Bhagalpur the insect population mainly consisted of hemipterans while at Rajmahal mayflies dominated the population. Bivalves formed the bulk of benthic population in the stretch, mainly represented by Lamellidens marginalis, Melania striatella tuberculata, Ammnicola, Bellamya bengalensis.
Fish and fishery
The River Ganges is the most important source of livelihood for a large number of fishers inhabiting its bank. The river system is reported to harbor about 265 species (Sinha, 2006). Of these 34 are of commercial importance, including Gangetic carps, large catfishes, featherbacks, and murrels. The upper river zone (Origin to Haridwar) is practically a non-fishing zone, while commercial fishing activity is mainly observed in potamon region of the river from Anupshahar in the State of Uttar Pradesh and downstream regions located in the states of Bihar and West Bengal (Jhingran and Ghosh, 1978). The fishery in the potamon zone of the river is mainly represented by the species belonging to families Cyprinidae and Siluridae. Recent studies of CIFRI (2008) and those reported by Jhingran (1974), Jhingran (1988) and Natrajan (1989) revealed the presence of 79 fish species belonging to seven orders and 25 families between Kanpur to Farakka stretch of the river. While during recent investigation (CIFRI, 2008) in the stretch between Kanpur to Patna alone, a total of 52 fish species were encountered in the samples from fisher's catches and experimental fishing carried out at different stations. However, these numbers are from the restricted middle stretch only.
The fish catch estimates at major fish landing centres in different stretches of River Ganges registered a declining pattern (Table 2). The major decline was recorded in major carps and hilsa. At Allahabad, during 1991 to 2000 the catches of major carps significantly dropped to a low of 6.65 t from 97.73 t estimated during the 1960s but seems to be regaining when in recent past a catch of 12.55 t has been recorded. But catches of large catfish continue to decline to almost 1/5th from 46.3 t to 9.02 t while the hilsa fishery has been reduced to negligible level from 22.35 t to just 0.22 t. Of late the total fish catches have registered some improvement mainly due to increased foothold of exotic fish species, especially Cyprinus carpio and Oreochromis niloticus, miscellenous species and a minor contribution from major carps as well.
At Buxar, hilsa was the main fishery in comparison to major carps during the period between 1963–1971. But with the commissioning of Farraka barrage this fishery declined sharply between 1972–1980 while there was a marginal improvement in major carp catches (Table 2). Later, between 1981–1986, the improvement in carps continued and may have been due to more fishing effort. Catches of hilsa dropped to just 1.01 t at the same time the miscellaneous fishery recorded an increase. Total fish catch from this centre registered improvement, but shift in species composition was a direct result of hydrological changes caused by barrage. Patna centre also recorded a drastic decline in major carp landings and when compared to the 1960s it was almost half during 1986–1993. The Bhagalpur centre also followed a similar trend. This clearly indicated that in the entire middle stretch of the River Ganges the fishery declined both in quantity and quality in time scale due to various anthropogenic factors. Gupta and Tyagi (1992) have also reported that the fishery is being harvested at much higher effort than the optimum fishing effort. Therefore, urgent steps are required to reduce the fishing pressure to achieve the goal of sustainable fishery from the river system.
Fish production pattern
The detailed analysis of the fish catches during the period has been reported by Jhingran and Ghosh (1978). Assessment of the catch per kilometer of river, 1961–1968, indicated significant variations among the stations (Table 3). During this period production of major carps was more at Allahabad and Kanpur; large catfishes dominated production at Varanasi, Patna and Bhagalpur, hilsa at Buxar and Ballia while Patna also recorded good production of miscellaneous species. This situation reflected upon variability and possible distribution of breeding and feeding grounds among different species in the middle stretch of the river system. During the same period the Patna recorded the highest per unit production (1803 kg km−1) contributed by miscellaneous species, large catfishes, major carps and hilsa in that order; perhaps a reasonably good situation at the time. But with subsequent changes in river ecology, the fishery production began to decline.
From 1972 onwards the fisheries recorded sharp changes in catches and hence in stock structure (Table 4). At Allahabad the yield dropped to 368.01 kg km−1 with a drastic decline in catches of major carps and large sized catfishes as well (Aorichthys aor, Aorichthys seenghala, Wallago attu). On the other hand, the catches of miscellaneous species recorded a marginal increase to (223.41 kg km−1).
It is observed that all economic species registered a declining trend from 1972 onwards. However, the major carps showed a marginal improvement during 1981–1990 which was due to good catches of Labeo calbasu, but it was short lived as later during 1991–2000 production of major carps dropped to just 28.91 kg km−1. During 2001–2006, the total fishery showed a general improvement, mainly due to invasion and production of exotic species, specifically Cyprinus carpio which is constantly increasing over the years. This indeed is very disturbing for the river system; in years ahead it may dominate and a similar situation has been reported from Dal lake in Kashmir by Vass (1998).
At Buxar the fishery showed serious decline from 1972 onwards mainly due to decline in hilsa catches. During the 1960s the fish yield at Buxar was 1329 kg km−1, out of which 918 kg km−1 was contributed by hilsa. After 1972 the hilsa fishery suffered a serious set-back and declined to 22.37 kg km−1 in 1981–1986. Similarly Patna which recorded maximum per unit yield of (1811.30 kg km−1) during the 1960s dropped to 783.94 kg km−1 during 1986–1993 and this decline has continued in recent times as well.
As compared to 1961–1970, the fishery in subsequent years at Bhagalpur stretch also registered a decline but not as severe as in other stretches. The yield rate during 1981–1988 declined to 663 kg km−1 from 870.6 kg km−1 recorded during the 1960s. The large catfishes and miscellaneous species registered a marginal decline but major carps and hilsa fishery suffered badly. The per unit yield of major carps dropped to 46.0 kg km−1 from 143.5 kg km−1 recorded during the 1960s while hilsa yield was only 7.1 kg km−1.
The dragnets, gill nets and hooks are commonly used by fishers to catch fish. Dragnets of two types small (less than 300 m in length) and large (>300 min length) are in use. The fishers use hook and lines in the upper stretch mainly and partly in the middle stretch; whereas traps are in use in some districts in Bihar stretch of the river system. Small scoop nets are used in the entire stretch but large ones are used only in lower stretches. Limited number of dip nets was observed to be in use by fishers at Allahabad and Mirzapur districts in Uttar Pradesh (U.P.)
About two thirds of gill nets in use were of smaller mesh size. The percentage use of lower mesh size gears was marginally more in U.P. Though no previous information is available about the percentage usage of different mesh sized gill nets by fishers, on interaction with fishers from different centres it can be inferred that in past the use of small meshed gears was minimal. Ray et al. (1966) reported that mesh size of gill nets varied from 18 to 26 cm and in some dragnet fishing more than 2 cm mesh was used.
In some districts of Bihar and Varanasi, and Ghazipur and Ballia districts of Uttar Pradesh, use of large dragnets of mosquito net clothing with minimal mesh size is common. These gears are highly destructive both to fish stocks and ecosystem as well.
In the recent past the use of dragnets, traps, hooks and lines has declined sharply as compared to the 1960s. At present the availability and use of gill nets has increased the manifold in all stretches.
Fish – As an energy harvest
The per unit estimates of fish yield from catch records and assessments in terms of energy, has been worked out on the basis of primary production estimates at different stations, using C-14 technique (Jhingran and Pathak, 1988). Subsequently, Pathak (1999) generated additional information in this regard.
The results indicate that there exists significant variation both in terms of stations and time periods in the transformation of available energy into potential per unit fish biomass. In this case the conversion ranges from 0.032–0.082 percent (Table 5). This would imply that in spite of available energy source at each station there are other parameters of ecosystem functions that are impacting the fish production as well. Further, the pattern of per unit fish harvest among different food niches in terms of energy worked out by Jhingran and Pathak (1988) and Pathak (1999) is set in Table 6.
The results indicate that across the stations there is a decline in fish energy harvest through the years (Table 6). This decline is also reflected in fish species sustaining on different food chains as well. However, through the years an increasing trend in energy harvest of miscellaneous fish species is a noticeable feature. This data set on estimated energy harvests of fish from different stations of the Ganges River does support that ecosystem functions have registered a significant shift, impacting the fish production as well.
Conclusions and suggested policy interventions
A steady decline in fishery both in quantity and quality is evident through the years in the middle stretch of the River Ganges. The food chain too has reflected the impact of ecosystem change. The ascribed causes for such a situation are habitat modifications due to catchment changes, increased water abstraction and creation of engineering structures on various tributaries of the river system. These modifications have triggered loss in original breeding and feeding zones of major fish species, difficulty in movement for migratory stocks, coupled with intensified fishing by large number of fishers has significantly dropped catch per unit effort resulting in sharp decline in total fish yield as well. The water quality at certain centres also impairs the health of fish stocks and ecosystem functions. The major issue of late is the drastic reduction in water flows downstream in a number of tributaries of the River Ganges (Vass, 2007). This reduction in flow has seriously impacted the ecology of these tributaries, which consequently has also affected the main river environment. All this has serious implications for the well-being of the fish both in the main river and the tributaries. The problems of river fisheries are further compounded due to non-implementation of recommended measures for its conservation, regulation and development. The Ganges is regarded as an inexhaustible self-renewable resource, available for unlimited exploitation with no need to conserve the stocks. All major rivers in the country are flowing through a number of states. Therefore, any conservation measures taken by any state will accrue benefits to other states as well. In this situation state(s) are not willing to invest in river conservation projects. To overcome this operational difficulty, the Government of India established “National Ganga River Basin Authority” in 2009, the highest policy body for River Ganges management. It is hoped that the present state of neglect of river fisheries in the country may be addressed through the support of this authority. Some of the suggestions to revive the dwindling fishery in this river system are highlighted below:
Hydrological improvement in connected wetlands and floodplains will enhance the breeding and recruitment of declining stocks.
To check the sediment flow, extensive plantation of native trees, shrubs, reeds, etc. on the river banks should be undertaken in respective states.
Mass awareness programs should be undertaken to educate the fishers about the ill effects of using destructive nets and catching of brooders and juveniles.
The impact assessment studies for future dams/barrage projects should be very thoroughly executed and recommendations of such studies should be strictly implemented by all stakeholders and monitored at highest level for any kind of violation.
Studies have shown that some of the exotic species, specifically C. carpio and O. niloticus have already invaded the Ganges River system and in some stretches their contribution has become quite significant. Stringent measures are necessary to avoid invasion by other exotic species so that the condition does not worsen.
Various schemes of government to improve river water quality are being implemented: should launch investigations to see if the fishery has improved at those centres as a result of such initiatives.
Rivers for fishery are almost neglected by States but urgent attention is needed to renew them as livelihood support system for landless fishers who cannot take up aquaculture.