Hariar Gop, Bangladesh – One ancient community in Bangladesh that uses otters to fish and lives in tandem with the Buriganga river is slowly disappearing because of industrial pollution and a decline of fauna in the water.

Rivers define Bangladesh as it lies at the end of one of the most densely populated river system on Earth. The waterways feed the country’s 150 million people, but the changing fortunes of these fishing communities represent the shifting sands of the river system, and the people who live along it.

Fishing with otters is a part of their livelihood, as the trained mammals lure fish into their nets. The practice has been in existence for about 1,500 years, but Bangladesh is perhaps its last bastion.

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However, for otter fisherman Bipul Kumar Bishwas, who lives near the western city of Jessore – about 140km southwest of the capital Dhaka – the situation has grown desperate.

“We’ve been doing this for generations,” he told Global News Insight. “The reason I learned this is because my dad fished with otters, my uncles did, everyone did. But now there aren’t really any fish left anymore, so the younger people aren’t learning this. They’re going to school and looking for other kinds of jobs.”

The otters are semi-domesticated and this unique livelihood has also helped preserve the species of smooth-coated otter, known by its scientific name Lutrogale perspicillata.

“Compared to when I was growing up, 90 percent of otter fishermen are gone. There’re maybe 50 to 60 boats left in this area that still fish with the otters,” Bipul said.

Craig A Meisner, director of World Fish Bangladesh, told Global News Insight that pollution from industry such as tanneries is also a major problem, adding to the depletion of fish stocks. It has turned the Buriganga river into one of the world’s worst environmental disasters in the world.

Follow Joseph Allchin on Twitter: @J_Allchin