The present status of ichthyofaunal diversity of river Ganga India: Synthesis of present v/s past

Abstract In India, large rivers are experiencing serious threat to aquatic biodiversity, and therefore flagship projects are being executed on freshwater biodiversity conservation using various methods and strategies. Ganga River is the largest and longest river of India supporting rich commercial and artisanal fisheries for decades. Periodical and systematic assessments of fish biodiversity of the large river ecosystem are important for effective conservation planning. Although over the years, the ichthyofaunal diversity of the river has been assessed under different programmes, however current assessment of fish diversity across different zones are not adequately studied and reported. In the present study systematic re-explorations were carried out and changing pattern of fish diversity and distribution during the period 2016–19 was recorded. We described a total of 190 fish species (182 indigenous and 8exotics) belonging to 133 genera, 62 families and 23 orders from upper Ganga (Harsil) to the river mouth of Hooghly estuary (Fraserganj). The assessment of native species revealed about 10% and 14.21% of the total species are listed under threatened status of IUCN Red List (version 2020) and CAMP (1998) threatened category respectively. Among the exotics, common carp (Cyprinus carpio) and tilapia (Oreochromis niloticus) was found dominated in upper, middle and part of lower stretch. The study showed considerable dominancy of major and minor catfish followed by small indigenous fishes. The evaluation of species richness through biodiversity matrices resulted the lower stretch to be the richest zone forming a strong cluster relationship (>0.71) among all the stations. The analysis of similarity percentage (SIMPER) of all the stations revealed an average similarity of 4.59% between all the stations. Shift in distribution pattern of few fish species was also recorded in certain sections of the river. The study indicated drastic decline of commercially important major carps and catfishes in comparison to previous records. The present paper also discussed about the potential threats and important guidelines concerning sustainable fisheries of River Ganga. The comprehensive information presented in this paper on fish diversity, distribution, abundance, production trend of major fish group of the river in different zones have highlighted relative change as compared to previous studies that will be useful for monitoring biodiversity and future conservation planning of the river basin.