Royal Manas National Park, BhutanAmong anglers, the golden mahseer is one of the world’s most prized catches. Up to nine feet long and golden-hued with big scales, it has a reputation as one of the world’s hardest fighting fish. Author Rudyard Kipling once wrote that the tarpin, another valued game fish, is “as a herring” in comparison to the golden mahseer. But this mythical carp is also hunted for food and has lost significant portions of its habitat, decimating its numbers throughout its southern Asian range.

Except here, in the idyllic Himalayan kingdom of Bhutan, where golden mahseer are thriving. Also known as the tiger of the river, the golden mahseer benefits—like other endangered species in the country, including actual tigers, white-bellied herons, and golden langur monkeys—from strong environmental protections and the religious reverence bestowed upon it.

“Bhutan has become the last stronghold of the golden mahseer,” says Dechen Dorji, who heads the World Wildlife Fund’s office in Thimphu, the Bhutanese capital. “It’s now up to us to protect this population and learn more about the species in order to ensure its future survival.”

That may seem like a tall task for a small nation like Bhutan, squeezed between India and China with a population of less than a million. But then this previously isolated kingdom, perhaps best known for its government philosophy of gross national happiness, is out to prove itself as a global conservation leader, which means protecting some of the world’s most endangered wildlife. (Read more: Bhutan could be a model for countries on the front lines of climate change.)

The mission is particularly urgent for wildlife living in freshwater. As a recent United Nations report on the global biodiversity crisis showed, the rate of species extinctions is accelerating more than ever before in human history. Since 1970, populations of freshwater species have declined by 83 percent, more than any other group, according to the Living Planet Index, a database managed by the Zoological Society of London in cooperation with WWF. Very big fish, like the golden mahseer, are particularly threatened by changes to river systems.

Under the king’s protection

The golden mahseer is listed as endangered on the IUCN Red List of Threatened Species. Overfishing and habitat loss have caused populations to decline by at least half in the species’ natural range, which stretches from Afghanistan in the west to Myanmar in the east. (Read about how river sanctuaries are helping fish recover in Southeast Asia.)

An omnivorous apex predator, the golden mahseer is believed to be able to grow nine feet long, though specimens longer than four feet seem to be rare today.

In Bhutan, it has long been forbidden to fish for mahseer, both golden and chocolate, a smaller but equally sparkling species. Not only are the rivers, which run from breathtaking elevations in the north to almost sea level in the south, considered sacred in the local culture, but the mahseer is also one of eight auspicious signs in Tibetan Buddhism, representing good luck. In the 1970s, the king at the time commanded his guards to protect mahseer spawning areas from poachers, who targeted it as a source of food. In 1995, the mahseer was listed as a protected species under Bhutan’s Forest and Nature Conservation Act.

Since then, mahseer populations in Bhutan have remained relatively undisturbed. There has been, however, very little scientific research on the fish. “It’s always been talked about in this almost mythical sense,” says David Philipp, a fish biologist and chair of the Fisheries Conservation Foundation in Champaign, Illinois. “People haven’t looked at it from an empirical or research perspective.”

That changed in 2015 when the Bhutanese government and the World Wildlife Fund contacted Philipp’s organization, on a directive from the current king, who wanted to learn more about the little-studied but much-revered mahseer.

Philipp, his partner Julie Claussen, a fisheries biologist, and their team set up a series of signal-receiving stations along the Manas River and its tributaries, no easy task in the inaccessible jungle terrain of southern Bhutan. Then over the course of two years, they captured, tagged, and released more than 60 golden and 40 chocolate mahseers. Those tags send back data to the receivers about where and how far the fish traveled.

For Tshering Dorji, the head ranger at Royal Manas National Park, the experience made him develop a new appreciation for the beauty of the mahseer. “I even stopped eating fish,” he says. Meanwhile, Deo Kumar “DK” Gurung, a senior forester at the park, is now “probably the best mahseer fisherman in the Himalayas,” Philipp says, because of his work catching mahseers to tag.

The data show that golden mahseers migrate longer distances and at greater speeds than anyone thought. In extreme cases, “we see these fish traveling 60, 70 kilometers in 24 hours and going through huge rapids,” says Claussen. “Their power is amazing.”

They also learned that mahseer use warmer, non-snowmelt tributaries for spawning, with individual fish returning to those exact locations annually. Curiously, the research also shows that the fish generally stay in Bhutanese waters and don’t move farther down into the Indian part of Manas National Park.

The team presented the findings at an international mahseer conference held in Thimphu at the end of 2018, which helped showcase Bhutan’s emerging conservation credentials. “In less than five years, Bhutan has become the leader in mahseer research and fish telemetry in the region,” says Philipp.

Finding balance

Still, the mahseer continue to face some threats in Bhutan. Increased public awareness and better law enforcement have helped to stem illegal fishing, but it remains a problem. Nearly half of the fish tagged for the study, for example, appear to have disappeared—some, perhaps, taken by poachers fishing for food, Phillip theorizes.

Also of concern is the impact of four new hydropower developments. Hydropower is a major source of revenue for Bhutan, which exports much of its power to India. These new developments, like existing ones, are so-called run-of-river projects, which are more fish-friendly than those that create dams. They’re also being built at higher altitudes, which the fish may not reach. But researchers warn that migrations could still be disrupted, and a recent government report recommended pausing construction of additional hydropower projects in the country.

Experts, including Philipp, Claussen, and Dorji, also warn that Bhutan should avoid stocking its rivers with mahseers bred in hatcheries, a common practice in neighboring countries such as India that are trying to replenish their populations. Stocked fish may spread disease and dilute the gene pool of wild populations. “The genetic imprint of the mahseer in Bhutan is very strong,” says Philipp. “Once you mix them with fish from hatcheries, those imprints are gone.”

Meanwhile, recreational fishing of mahseer is expected to be introduced soon in the kingdom, in an effort to boost ecotourism revenues. To safeguard its environment and culture, Bhutan has long maintained a policy aimed at attracting fewer but higher-spending tourists. All visitors to Bhutan must pay a daily fee of between $200 and $300, which covers the costs of food, accommodation, and other basics, with $65 of it going to a social welfare fund. Well-heeled foreign sport fishers are seen as the ideal customers.

While sport fishing appears to be at odds with Buddhist culture, which maintains that no animals should be harmed or killed for pleasure, catch-and-release fishing for trout is already permitted in Bhutan, though under strict regulations. No fishing is allowed in national parks or other protected lands, which make up more than half of the country, or near temples. The guidelines for fishing mahseer are expected to be even more restrictive.

“We want to make sure we come up with a program that benefits the mahseer and at the same time benefits people here,” says Dorji, the WWF representative. “It is important to find the right balance.”