Fish diversity in Ganga up 36% in 10 years

KOLKATA: Fish diversity in the Ganga had nearly halved in 20 years between 1991 and 2012. But it now appeared to be on the mend, with over 90% of endangered species making a comeback following interventions to clean up the river and sensitising fishermen to avoid catching juveniles. Prized fish like hilsa, kajri or sutri, vacha, garua and morari or piyali were among species that have revived—and available now in towns along the river.
Studies conducted over the past five decades reveal a wave-like curve: 207 species in the inaugural study in 1974, rising to 266 in 1991 before witnessing a precipitous decline to just 140 in 2012 and then making a smart recovery to 190 in 2021, a 36% rise in the last decade. Researchers have looked at the river’s primary channel, not its tributaries and distributaries.
Officials at the Central Inland Fisheries Research Institute (CIFRI) clarified that the fish species that dropped out of the records did not disappear from the river altogether but were not in sufficient numbers. These include pabda, batashi, kholshe, deshi koi and deshi magur.
In earlier studies, 79 native Gangetic fish species were detected in the stretch between Kanpur in UP and Farakka in Bengal. But the latest study reported 103 species in the same stretch. The lower zone from Farakka to Tribeni in Bengal reported 123 species and 72 along the freshwater tidal stretch, with the dominant species being Hilsa and other small indigenous fish such as chella, morari, Gangetic river sprat and Indian river shad.
The improvement in fish diversity and population followed multiple initiatives taken by CIFRI, including ranching and seed production of indigenous Gangetic species. More than 47 lakh fingerlings of major Indian carps have been ranched to increase diversity.
The effects of ranching are beginning to show. Landing data from different Ganga ghats showed a rise in fish stocks. The increase in fish population has, in turn, helped improve the water quality.
Fishermen Purna Patra from Godakhali and Binay Biswas from Tribeni said their catch had increased significantly over the past few years. “Local varieties of fish that were rarely found are now being netted,” said Biswas.
The Farakka region recorded 84 species, the highest ever for that stretch, indicating congenial riverine environment supporting a stable fish population. “In the lower Bengal stretch of the Ganga, four exotic fish species — crocodile fish, bighead carp, grass carp and silver carp — were reported, exhibiting population stability in the river largely due to change in riverine ecology,” said CIFRI director and project investigator Basanta Kumar Das.
The decline between 1991 and 2012, scientists at CIFRI said, was due to deterioration in the river’s water quality because of outflow of polluted water, sewage and chemicals from civic bodies and industries along the river, and overfishing, which impacted the overall fish population.
ICAR-CIFRI, along with other agencies engaged in the Ganga Action Plan project that was later rechristened National Mission for Clean Ganga, has managed to stem the decline and revive 50 species. But there are still less-abundant species like pangasius, pabda catfish, giant river goonch, chitala and silond catfish that require more effort. Around 10% of the native species are considered threatened, while 15 more are in the near-threatened category, two vulnerable and two endangered as per the IUCN red list 2020.