Riverine fisheries are of particular importance in the tropical regions as they provide food and nutrition to millions of people and support their livelihood.
The Brahmaputra changes its course and pattern along with its current flow very frequently especially in its upper stretches and this has a strong bearing on its hydrobiology. The hydro-geological pattern of the Brahmaputra has resulted in a possible zonation of the river into five major types of fish habitat. Altogether 167 fish species have been recorded from the upper Brahmaputra of which about 30 percent may be considered as ornamental varieties. Again, according to their seasonal availability, the fish fauna has been grouped into four principal categories. Among all the hydrological factors, flood impulse is probably the strongest factor that regulates other limnological conditions and faunal distribution. Usually, there are three or four high floods between May and October and fish migration is intimately related to this flood regime.
During the dry season fishing is mostly restricted to near the confluents of tributaries or channels and also at river meanders. However, large-scale felling of trees in the catchment areas and construction of embankments along the river banks have altered the riverine ecosystem drastically, as a result of which, the river has become heavily silted and the connecting channels of the floodplain lakes are also dammed. Consequently, fishes and other megafauna are deprived of adequate water cover, food supply and breeding grounds. An ecohydrological approach has been advocated for habitat restoration.
Extensive surveys were conducted to explore the diversity of fishes, distribution patterns, abundance, threat, and habitat status in the upper, middle, and lower stretch of river Gomti, a tributary of river Ganga. Altogether 56 fish species belonging to 20 families and 42 genera were collected from various sampling sites. Of the 56 species, five belong to the 'endangered' (EN) category and 11 belong to the vulnerable (VU) category. Six major categories of habitat were identified and pattern of fish assemblage and dominant genera in each habitat studied. Apart from Indian Major Carps (Labeo rohita, Catla catla, Cirrhinus mrigala), Chitala chitala, Notopterus notopterus, Ompok pabda, O. bimaculatus, Labeo bata, L. calbasu, Cirrhinus reba, Channa marulius, Bagarius bagarius, and Clupisoma garua were the important species. All the species have been reported for the first time in this river. Indiscriminate catch, poisoning, using of fine mesh sized nets, dumping of sewage, siltation, water abstraction, changing land use pattern, decreased water discharge, and exotic species threaten the fish diversity. Urgent need exists for taking up research on the priority fish species and their habitat. Restoration measures have been proposed based on ecosystem scale approach for fish biodiversity conservation.
Source: http://link.springer.com
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