Freshwater fish outnumber salty cousins

CONTRARY to popular belief, there’s not a lot of fish in the sea, say researchers.

Despite covering 70 per cent of the Earth’s surface, marine environments contain only 20 per cent of all its species.

In the new study, scientists made the surprising discovery that freshwater rivers and lakes contain more fish species than salty oceans. Yet freshwater environments occupy only 2 per cent of the Earth’s surface.

The findings suggest that most marine fish alive today are descended from freshwater ancestors, even though life is thought to have first evolved in the oceans. A marine apocalypse may have been followed by a re-emergence of life in watery environments on land.

The findings are published online in the journal Proceedings of the Royal Society B.

A team led by Dr John Wiens, from Stony Brook University in New York, studied the biodiversity of ray-finned fish, 96 per cent of all fish species.

“There are more fish species in freshwater than in saltwater habitats, despite the much greater area and volume of the oceans,” said Dr Wiens.

“More remarkably, our results suggest that most marine fish alive today are descended from freshwater ancestors.”