Meet Boramy — a female giant freshwater stingray weighing 661 pounds, caught in the Mekong River in Cambodia in 2022. She is the largest freshwater fish ever recorded. After scientists tagged her, she was released back into the river.
They are among the most extraordinary animals on Earth — ancient, enormous, and almost entirely unknown to the public. Giant freshwater fish: the Mekong giant catfish that can weigh 600 pounds, the arapaima that can stretch nine feet long, the giant freshwater stingray that lurks in the deep pools of the Mekong and Chao Phraya rivers. These species have survived for millions of years. They are now among the most endangered animals on the planet.
In June 2022, a female giant freshwater stingray was caught by fishers in the Mekong River in northern Cambodia. Scientists rushed to the scene, measured and tagged her, and released her back into the river. She weighed 661 pounds — the heaviest freshwater fish ever recorded anywhere in the world. They named her Boramy, the Khmer word for "full moon." The discovery made headlines globally. But behind the wonder lay a sobering reality: this magnificent animal belongs to a species whose populations are in freefall, threatened by dams, sand mining, overfishing, and habitat destruction.
Giant freshwater fish are the largest animals in rivers — and among the least known. Many are critically endangered. Most people have never heard of them.
Giant freshwater fish are what scientists call megafish — species exceeding 66 pounds. They occupy the top of river food webs, regulate fish populations, transport nutrients across vast distances, and serve as indicators of river health. When megafish disappear, it signals that something is fundamentally broken in the ecosystem. Yet they receive a fraction of the conservation attention devoted to iconic large mammals like elephants or tigers. They are invisible — living underwater, in remote rivers, in countries with limited resources for environmental monitoring.
The world's megafish are found primarily in the great river systems of Asia, South America, and North America. Many have been in steep decline for decades. The Mekong giant catfish — perhaps the most emblematic of all — was once common across the river's full length. Today it is critically endangered, with wild populations reduced to a small fraction of their historical numbers. The arapaima of the Amazon basin, one of the largest scaled fish in the world, has been heavily overfished throughout its range. The giant freshwater stingray, only recently confirmed as the world's largest freshwater fish, is poorly understood and rarely studied.
Part adventure story, part conservation argument, Chasing Giants takes readers to some of the most remote and imperiled river systems on Earth in search of the giant fish that inhabit them. Co-authored by megafish biologist Zeb Hogan — host of National Geographic's Monster Fish — and journalist Stefan Lovgren, the book traces the decades-long effort to document, understand, and protect the world's largest freshwater species before they disappear.
From the deep pools of the Mekong to the floodplains of the Amazon, Chasing Giants reveals a hidden world of extraordinary animals and the urgent science trying to save them.
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