The elusive river shark: a predator that was once presumed extinct

Nature · Published 3 October 2026 Swipe more like this →

In short: True river sharks of the genus Glyphis are among the most mysterious creatures in our waters. Often confused with the more common bull shark, these rare predators were thought to have vanished entirely until the late 20th century, when researchers finally confirmed their survival in remote corners of Australia and Borneo.

The genus Glyphis represents a specialized group of sharks that inhabit freshwater and coastal environments across South Asia, Southeast Asia, New Guinea, and Australia. Unlike the bull shark, which is frequently misidentified as a river shark due to its ability to traverse similar habitats, the true Glyphis genus remains elusive. Their secretive behavior has made them notoriously difficult to study, leading to ongoing scientific debate regarding their taxonomy. While researchers once believed there were five distinct species, modern molecular analysis suggests that some, such as the Bornean and Irrawaddy river sharks, may actually be variations of the Ganges shark, Glyphis gangeticus.

The life cycle of these sharks is tied to specific environmental conditions. They are typically found in muddy, low-salinity tidal zones, with evidence suggesting they give birth around October. Their habitat preferences vary by species; for instance, the Ganges shark is strictly a freshwater dweller, whereas the speartooth shark and the northern river shark are known to navigate both tidal reaches and coastal marine waters. The speartooth shark, in particular, thrives in fast-moving, highly turbid environments, sporting a distinctively broad snout and tiny eyes that suit its murky surroundings.

Despite their resilience, these populations face significant threats. The Ganges shark, which utilizes the Ganges River as a vital nursery, has seen its numbers plummet due to pollution and historical fishing pressures. India remains a major contributor to global shark and ray landings, accounting for approximately nine percent of reported captures. Because these sharks were only rediscovered in the late 1900s, much of their biology remains a mystery. Understanding their distribution and population health is critical, as they represent a unique evolutionary lineage that is currently struggling to survive in some of the world's most heavily impacted river systems.

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