Shantas Das was busy repairing a fishing net with two other fishermen at Shamlashi Beel, a wetland connected to the Buriganga River. For Shantas, who supports a family of six, his boat and nets — worth around Tk200,000 — are his only means of survival. 

That day, however, he was forced to mend the net after it was badly torn by an invasive species formally known as the suckermouth catfish, locally called ‘sucker fish’.

“Day by day, the number of these fishes in the Buriganga and its surrounding area is increasing,” Shantas said.

Another fisherman with him, Mohammad Razab Ali, echoed the concern, “Today we caught at least five maunds of sucker fish in our net, but the fish we could actually sell weighed only six to seven kilos and earned us just Tk1,200.”

However, Shantas explained that the situation was very different just a few years ago. 

“Seven or eight years ago, this fish suddenly started to spread. My family has been fishing in the Buriganga for generations. Pollution reduced the number of native fish, but we could still survive by fishing in this wetland beside the river. Now these new monsters have arrived,” he said. 

“Earlier, we used to sell Tk5,000–6,000 worth of fish every day. Now we sell only around Tk1,000,” he added.

The sucker fish was first introduced to Bangladesh in the 1980s as an aquarium species. With its hard, armoured body and suction-cup mouth, it was marketed as a “cleaner fish” that feeds on algae inside glass tanks. Over time, many aquarium owners released the fish into nearby water bodies, unaware that it could survive, breed, and spread aggressively in the wild.

In Bangladesh, the first known sighting dates back to the mid-1980s in Gulshan Lake, though it went unreported at the time. Scientific identification came much later, in 2008, when researchers confirmed the presence of the Orinoco sailfin catfish in Bogura. Since then, media reports and field observations have documented the species across almost every type of freshwater habitat — rivers, ponds, lakes, haors, beels, canals, ditches, and even paddy fields — demonstrating its ability to thrive regardless of depth, flow, or seasonal variation. However, the number was very minimal.

Originally native to freshwater rivers and streams of Central and South America, particularly the Amazon Basin, the sucker fish has proven exceptionally adaptable. It can survive in fast-flowing or stagnant waters, polluted environments, and low-oxygen conditions, as long as freshwater and organic matter are present. This ecological flexibility, combined with rapid growth and early maturity, has allowed the species to spread far beyond its natural range, raising serious concerns about biodiversity loss.

A 2023 study published in the Bangladesh Journal of Zoology, titled “Invasive Suckermouth Catfishes in Bangladesh Wetlands: Present Status and Challenges”, notes that the first confirmed record of the species in open waters dates back to 2008. Since then, it has quietly colonised rivers, canals, lakes, haors, beels, and even paddy fields across the country.

Unlike native fish, sucker fish grow quickly, mature early, and thrive even in polluted or low-oxygen waters like the Buriganga. Their bony, armoured bodies protect them from predators, while their sharp spines tear fishing nets and injure birds and animals that attempt to swallow them. Researchers warn that the fish uproot aquatic plants and burrow into riverbanks, accelerating erosion and destroying breeding grounds of indigenous species. As their numbers increase, small native fish — many already under threat — are pushed out by competition for food and space.

The study also notes that fishermen frequently find their nets filled with sucker fish that have little to no market value. Removing them consumes time, damages equipment, and leaves less space for valuable species such as koi, shing, and punti. The study documents the presence of sucker fish in at least 17 rivers, including the Buriganga, Turag, Shitalakshya, Padma, Halda, and Meghna, with higher concentrations around urban centres where aquarium dumping is more common.

An analysis of media reports from 2009 to 2023 shows a sharp rise in sightings after 2020, peaking in 2022. The spread is most concentrated around Dhaka, Chattogram, and Khulna, suggesting that aquarium dumping in cities has been a key driver of the invasion. Reports now span dozens of districts and at least 17 major rivers, indicating that it took nearly two decades for the species to become fully invasive.

Recognising the growing threat, the government banned import, breeding, sale, transport, and possession of sucker fish in 2022. However, researchers warn that eradication will be extremely difficult, as the species is already firmly established in open water systems.

A few minutes’ walk from Shantas, on the far side of the beel, 62-year-old Mohammad Babul Hossain operates several boats and hires labourers to catch fish.

“Every year, the number of sucker fish increases,” he said. “In the past, if we invested Tk10,0000 for a season, we could earn around Tk70,000 in revenue. Now we don’t invest that much, because we barely make a profit of Tk10,000 to Tk20,000.”

He added, “If we go fishing and there are 10 kilos of deshi fish we can sell, our nets will contain more than 300 kilos of sucker fish.”

Banning import and trade was necessary, but it came too late. Without a national action plan that combines strict enforcement, scientific monitoring, public awareness, and financial incentives — where the government can buy the invasive fish from fishermen and dispose of it safely by burying it — the situation will continue to worsen. This is currently the only viable way to reduce the population and protect native species.

Md Hasan Faruque, Associate Professor, Department of Fisheries, University of Dhaka

Rashed Khan, a seasonal labourer from Netrokona working for Babul this season, said the fish cause serious injuries. Holding up both hands, marked with deep cuts, he added, “These fish hurt a lot. Our nets catch hundreds of them, and then we have to throw them back into the water because it’s impossible to kill them all. So our work doubles without any additional benefit.”

Evidence of their claims was visible along the banks of the beel, where numerous sucker fish lay dead.

“When it first became common, we even tried making dried fish, but it didn’t work,” Babul said. “It’s not edible and it’s of no use for anything. Slowly, it’s destroying our lives. Who knows what will happen in five years? Still, we haven’t received any help from the government or any authority. It spreads heavily in the wetlands in Keraniganj and Savar.”

Unlike native fish, sucker fish grow quickly, mature early, and thrive even in polluted or low-oxygen waters like the Buriganga. Photo: Saqlain Rizve

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Unlike native fish, sucker fish grow quickly, mature early, and thrive even in polluted or low-oxygen waters like the Buriganga. Photo: Saqlain Rizve