The discovery of a new stronghold for the rare Ganges sharks in Indonesia brings back hope for their protection

Ganges sharks are extremely elusive creatures, living in murky, brackish waters. They are one of only three species of river sharks in the world and are almost impossible to see in their natural habitat.

Ganges sharks have never been photographed alive, and biologists' only evidence of their existence is the occasional bycatch. Even then, they may only find a fin.

This critically endangered species lives in parts of Pakistan, India, Bangladesh, Malaysia and Myanmar, but the majority of its numbers are believed to be declining.

Only 240 adult fish are estimated to remain, according to the International Union for Conservation of Nature's Red List of Threatened Species.

The last documented sighting of a Ganges shark near the river that bears its name was in 2017.

But after decades of sporadic sightings across South and Southeast Asia, the last stronghold of Ganges sharks may have been found in a remote corner of Indonesia.

New fieldwork now offers new hope that it has a future there.

In 2023, researcher Michael Grant from Australia's James Cook University led an expedition with partners from Borneo Tarakan University and Hasanuddin University to North Kalimantan.

The Indonesian island of Borneo was not known to be within the range of these sharks, but while visiting a village on the banks of the Sisayap River, Grant met a fisherman who accidentally caught 17 of these sharks in just one week.

Grant said this number exceeds what has been observed worldwide in the past 20 years.

He added: "We suspected that these fish existed in the rivers of Borneo, but no one had ever gone looking for them before."

For her part, Binaya Simeon, an Indonesian doctoral student at Charles Darwin University, who was part of the mission, confirmed that “the discovery was very exciting and important.”

Simeon had previously spotted other river shark species in pristine areas of Australia's remote Northern Territory.

“Honestly, I didn't think we had this kind of habitat left in Indonesia, especially in North Kalimantan, especially when taking into account factors like population density, pressures from mining, palm oil plantations, and other development projects,” she explained.

The discovery has prompted the IUCN Shark Expert Group to classify the Sisayab River as an Important Area for Sharks and Rays (ISRA) in 2024.

In May, the team of researchers returned to conduct further research and launch efforts to protect what Grant described as “possibly the world’s last viable population of these organisms.”

He said: "This was a great success, as most of the communities we spoke to expressed their happiness to be responsible for caring for this type of fish."

Fortunately, Grant believes it is unlikely that this group was intentionally exploited.

“There does not appear to be any reliance on these fish as a means of earning a living, nor are they of cultural importance,” he explained.

He added that the villagers do not like its taste, while its delicate fins are considered unattractive in the Asian shark fin market.

Therefore, the risk of these species being poached or traded is small.

Unfortunately, these sharks are still killed accidentally.

It is worth noting that the problem of bycatch goes beyond just one fisherman, as field studies conducted in 2026 revealed additional evidence of the presence of Ganges sharks, bringing the total number to 42 fish between the two trips, although the majority of them appeared in the form of fins found dried in villages.

The cause of the death of these fish is still unclear.

“Fisheries are highly variable,” Grant explained, noting that fishermen may be targeting other species, using gear that increases the likelihood of bycatch of Ganges sharks.

Grant saw legislation, whether banning specific fishing gear or creating no-hunt zones before changing fishing practices, as critical.

The number of Ganges sharks found in North Kalimantan is “extraordinary,” said Save Our Seas Foundation scientific advisor Sarah Fowler, who was not involved in the research.

She also expressed concern that shark populations could be affected by the growing threat of bycatch such as the dried fish bladder industry, which generates billions of dollars.

Dried fish bladder is considered a delicacy in China, and some of it is extracted illegally.

Fowler has heard that fishing vessels are heading to areas in Kalimantan where sustainable fishing has been practiced for generations.

She added that Ganges sharks are "extremely endangered."

How can a ghost-like object be protected?

So, how can these species of organisms be protected when they are almost impossible to study? This is the dilemma faced by Ganges shark specialists.

“We still have very limited data on this species, but at the same time we are racing against time to avoid extinction,” Simeon said.

Simeon pointed out that although there are no scientific records of the presence of Ganges sharks in the area before 2023, local residents must have known about their presence for generations.

“For me, this is a reminder that modern science cannot succeed alone,” she said.

She stated that the willingness of local residents to protect this species “needs support from scientific bodies and the government,” calling for incentives such as improving educational facilities, health care services, or other services.

Simeon believed that protecting this species would be a difficult task, but not impossible.