Sharks more likely to sink than swim in freshwater: study

19 January 2015 - 18:01 By Times LIVE

Sharks rarely evolve in freshwater, because they would generally struggle not to sink according to new research

IFLScience reports that while Cartilaginous thrive in marine ecosystems across the planet, very few have evolved to live in lakes and rivers.

the the thousand species of Elasmobranchii (sharks, rays and skates) about 50 live in freshwater, and most of them are part timers.

For the most part researchers suspect that it might be the metabolic costs involved in having to maintain the right pressure by controlling the amount of water and salt in their bodies.

However new research published in the Journal of Experimental Biology points to buoyancy as another potential factor.

Stanford's Adrian Gleizz and his colleagues designed hydromechanical model based on the bull shark, one of those few part timers.

What they found was that freshwater leads made the sharks two to three times less buoyant.

That means they have to struggle a lot more to stay off the bottom of the lake.