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Articles by R. K. Tyagi
Total Records ( 2 ) for R. K. Tyagi
  K. K. Vass , R. K. Tyagi , H. P. Singh and V. Pathak
  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.
  M. K. Das , A. P. Sharma , K. K. Vass , R. K. Tyagi , V. R. Suresh , M. Naskar and A. B. Akolkar
  The Ganges River is one of the largest river systems in the world and sustains a rich biodiversity of fish and fishers. In recent years, a decline in fish diversity and catch has become apparent due to various anthropogenic activities in the river basin. This study analyses the current fish diversity, distribution and community structure along the longitudinal gradient of the river and evaluates the ecological integrity of the riverine stretch applying a multimetric assessment approach. One hundred forty three fish species were recorded from the river and Cyprinidae was the dominant family. The middle stretch of the river exhibited dominance of small bodied erytopic, indigenous and exotic fish species with periodic and opportunistic life history strategies with significant decline of the large bodied prized Indian major carps. A tropic shift towards dominance of carnivore catfish species is evident. Non-metric multidimensional scaling revealed greater distribution and abundance of fish species with increasing river width and depth, higher sediment organic carbon, silt and clay along the river gradient. A significant change in the catches composition was evident from 1961 to 2010 in the middle stretch of the river at Allahabad. It reflected a progressive decline in proportion of Indian major carps (IMC) and the anadromous Shad Tenualosa ilisha and a significant increase in the proportion of exotic fish Cyprinus carpio and Oreochromis niloticus which represented 43-48% of the total catch. Assessment of biotic integrity showed that 28% of sample locations in the river supported fish assemblages under acceptable conditions.
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