The Ujani reservoir, once famous for its high-quality freshwater fish, is now battling an ecological crisis triggered by invasive alien species – the suckermouth catfish, Tilapia, and African catfish. These foreign fish have decimated native biodiversity, collapsed local fish populations, and put the livelihoods of thousands of fishermen at risk. In response, the Bombay Natural History Society (BNHS) has launched an active removal and native-restocking programme, marking India’s first such community-driven initiative.Speaking to The Indian Express, Dr Unmesh Katwate, ichthyologist (Scientist B) at BNHS, said the suckermouth catfish is native to the Amazon River in South America and entered India through the global aquarium trade. “As this fish is put to clean aquariums, and when they grow in size and become a menace to other fishes, instead of killing them, they are usually dumped into canals, streams or rivers,” he said.Once in the wild, the species, locally nicknamed the Helicopter fish’ for its unusual appearance, proved highly destructive. “It feeds on fish eggs, burrows into river banks and earthen check dams, while outcompeting native bottom-feeders,” Katwate said, adding that since the fish is not fit for human consumption, fishermen would simply throw it back into the reservoir or discard it as waste.A reservoir overrun by invasive speciesThe scale of the takeover is stark. “Over two decades ago, one used to find only native fish in Ujani, but now around 97 per cent found are alien fish that include suckermouth catfish, Tilapia, and African catfish, and the rest, just 3 per cent, are native fish,” Katwate said. Of that 97 per cent alien population, suckermouth catfish alone accounts for roughly 30-40 per cent.Must Read | The surprising threat lurking beneath a Philippine lakeThe species’ burrowing habit, used for breeding, is also weakening the reservoir’s infrastructure. “For breeding, these fish had to create burrows along the river bank, which eventually is eroding the Bhima river bank, and has the potential to create structural damage to earthen dam walls,” Katwate said. He noted that the fish is remarkably adaptable to adverse conditions, having been found as far as the origin of the Bhima river in Bhimashankar.Livelihoods under threatThe invasion has hit Bhigwan’s fishing community hard. Bharat Mallav, a fisherman from Bhigwan, said over 20,000 fishermen, traders, transporters, and labourers depend on the reservoir for their livelihood, and all of them are now under threat. “Just around five years ago we used to get surprised to see suckermouth catfish in our nets because of its strange appearance,” he recalled.Today, the fish is a routine, costly nuisance. “Sucker fish get entangled in our nets, so while removing them we have to cut that specific patch, and because of this we are bearing an additional burden to change the fishing net every 15-20 days for Rs 1,500,” Mallav said.Story continues below this adDatta Pawar, a fisherman from Dalaj with eight years of experience on the reservoir, described how the invasive species have altered daily catches. “Extricating the sucker fish from nets is difficult and time-consuming, slowing down fishing operations and reducing daily yield,” he said.“Of our daily catch, around 70-80 per cent is Tilapia and Sucker fish, and the remaining is Rohu, Catla, and Mrigal, which actually helps in earning,” Pawar added that the dominance of alien species has sharply worsened our earnings over the last two years, as native stocks like major carps have declined due to competition and predation.Nitin Dole, a resident of Kumbhargaon whose 35 acres of ancestral farmland were acquired for the Ujani Dam project, pointed to a longer history of stress on the reservoir. “Ujani reservoir is well known for its high quality freshwater fish, but since the last over three decades we are battling with rising water pollution, illegal fishing with fine-mesh nets that capture small fish, including fish seeds, and destroy potential production, then illegal hatchery of Mangur fish along the dam, and now lately with dangerous alien fish species that’s threatening the ecosystem,” he said.BNHS’s solutionTo tackle the crisis, BNHS inaugurated India’s first community-driven suckermouth catfish collection centre at the Bhigwan fish market on April 7. The initiative offers fishermen a financial incentive to collect and hand over the invasive fish rather than discard it.Story continues below this ad“To encourage fishermen to collect the fish, we are currently offering Rs 2 per kg above the auction rate as an incentive,” Katwate said. “And now we have helped create a market and micro-economy so fishermen earn an average of around Rs 30-35 per kg at Bhigwan market.”The results so far have been significant: over 36 tonnes of suckermouth catfish have already been pulled out of the Ujani reservoir. The collected fish is sent to oil mills in Taloja and Ratnagiri in the Konkan region, where it is processed, and the resulting suckermouth fish molasses is used as fertiliser for plants.A first-of-its-kind effort in IndiaAccording to Katwate, similar suckermouth catfish infestations have been reported in the United States, but India’s Bhigwan initiative is the first organised removal programme of its kind.He stressed that the fight is far from over. “I feel that the government should look upon the aquarium trade and ban such imports,” he said. “Put in funds that would help to more effectively manage alien species in regions beyond Bhigwan. Also, the efforts should be long-term, like around 10 years for a lasting impact.”