Mongabay · Climate & nature

Freshwater Sharks and Rays Face High Extinction Risk

Dozens of shark and ray species inhabit freshwater environments but are poorly studied and protected, leading to a high extinction risk, particularly in the Indo-Pacific region.

Globally, around 60 shark and ray species spend part of their lives in inland waters. In the Indo-Pacific, 76% of these non-marine species are threatened with extinction, double the rate of marine relatives. Threats include dams, pollution, and habitat loss.

These species, known as euryhaline elasmobranchs, can tolerate varying salinity levels, allowing movement between marine and freshwater habitats. Some, like South American freshwater stingrays, are obligate freshwater species.

Scientific knowledge of these species lags significantly behind marine counterparts, with critical data on reproduction, movement, and population structure often missing. Remote river locations make research difficult.

South America's river basins host remarkable freshwater elasmobranch diversity. These species are vulnerable to habitat fragmentation from dams and mining, with slow growth and low reproductive rates exacerbating their risk.

The aquarium trade also pressures some species. Climate change, including rising temperatures and altered flood cycles, adds further uncertainty to their survival.

Recent studies reveal greater mobility in some species, suggesting that habitat fragmentation and dams could impact populations on a larger scale than previously understood.

Scientists refer to these river species as 'forgotten fauna,' emphasizing that conservation efforts have largely overlooked them compared to marine species. This neglect poses a significant risk of losing unique creatures.

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