Kolkata, Jan 15 (PTI) Fish diversity in the Ganga has increased by nearly 61 per cent over the past 11 years, reflecting sustained ecological recovery under government-led rejuvenation efforts, a study by the ICAR-Central Inland Fisheries Research Institute (CIFRI) has revealed.
The river also recorded its highest fish diversity in nearly five decades, with scientists documenting 230 fish species across its various stretches, the research found, highlighting the impact of ongoing restoration and conservation measures.
CIFRI Director BK Das said, “This is the result of a number of rejuvenation plans over the years, including the ongoing Namami Gange.” The fish diversity increased from 143 in 2012 to 230 in 2023, a rise of 60.83 per cent. Besides, the latest survey, conducted in 2023, recorded the number of species to 230, the highest diversity in over half a century.
ICAR-CIFRI’s Fisheries Resource Assessment and Informatics Division head Srikanta Samanta said, “The Ganga rejuvenation plan, starting from the Ganga Project Directorate in the 1980s to the present National Mission for Clean Ganga, has significantly improved the ecology of the river.” The Ganga, which originates in the Himalayas and flows for about 2,525 km through Uttarakhand, Uttar Pradesh, Bihar, Jharkhand and West Bengal before entering Bangladesh and draining into the Bay of Bengal, once supported a far richer aquatic ecosystem. Historical records show that the river hosted 271 fish species in 1822, but that diversity declined steadily over time due to pollution, habitat degradation and overexploitation.
By 1974, the number of species had dropped to 207, falling further to 172 in 1991, and touching a low of 110 species in 1998. Following intensified restoration and fisheries management efforts led by Barrackpore headquartered ICAR-CIFRI, fish diversity improved to 162 species in 2004, before slipping again to 143 in 2012.
Explaining the broader ecological improvements, Samanta said the recovery of fish diversity has been supported by better water quality and habitat conditions across the river.
“Although the population has increased significantly by this time, the riverine habitat has not deteriorated; rather, it has improved,” he said.
He pointed to a marked improvement in dissolved oxygen levels, particularly in the middle stretches of the Ganga, compared with the 1980s.
“Oxygen availability in water is nearly a thousand times lower than in air, which makes aquatic ecosystems far more vulnerable. Monitoring water quality is therefore critical for maintaining ecological balance,” Samanta said.
Region-wise, the highest species counts were recorded in Uttar Pradesh, with Bijnor (109 species) and Narora (93) emerging as biodiversity hotspots. In West Bengal, Farakka recorded the highest number of species at 85, followed by Berhampore (76), Frazerganj (70), Balagarh (66) and Tribeni (63). In contrast, Diamond Harbour (38) and Gadkhali (32) showed considerably lower diversity.
As part of the basin-wide assessment, ICAR-CIFRI scientists collected fisheries and ecological data from 33 tributaries and six floodplain wetlands across the Gangetic basin, allowing a comprehensive evaluation of the river’s biological health.
Officials said stock enhancement and ranching programmes played a key role in the revival of fish populations. ICAR-CIFRI carried out 167 ranching activities, releasing 203.4 lakh fingerlings of Indian Major Carps–Rohu, Catla and Mrigal–along with Mahseer, into the river system. The release of fish spawn and eggs into river waters was aimed at stock enhancement, ranching and restoration of riverine fisheries.
“The impact of ranching is clearly reflected in the increased landings of Indian Major Carps, with rises of 24.7 per cent at Prayagraj and 41 per cent at Varanasi compared to 1959,” officials said, describing the data as evidence of the effectiveness of stock enhancement interventions.
Significant progress has also been recorded in the restoration of Hilsa, a key migratory species. Since 2010, around 3.8 lakh adult Hilsa have been released upstream of the Farakka barrage, of which 6,031 fish were tagged.
The recovery rate of tagged Hilsa stood at nine per cent, with the species being traced as far upstream as Ballia in Uttar Pradesh, indicating a gradual extension of its migratory range over time.
In addition, 54.9 lakh fertilised Hilsa eggs and 8.1 lakh Hilsa spawn were released upstream of the Farakka barrage to strengthen natural breeding and improve the river’s Hilsa population.
Samanta further noted that pollution indicators have shown sustained improvement.
“The presence of metals and pesticides in the Ganga is now well below the permissible limits,” he said, adding that, like the river Ganga, river-specific plans will definitely improve our inland aquatic environment,” Samanta said. PTI BSM NN
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