Freshwater fish are in "catastrophic" decline with one-third facing extinction, report finds By Sophie Lewis Giant Chinese paddlefish declared extinct Thousands of fish species are facing "catastrophic" decline — threatening the health, food security and livelihoods of hundreds of millions of people around the world. New research shows that one-third of all freshwater fish now face extinction. According to a report published Tuesday by 16 global conservation groups, 18,075 species of freshwater fish inhabit our oceans, accounting for over half of the world's total fish species and a quarter of all vertebrates on Earth. This biodiversity is critical to maintaining not only the health of the planet, but the economic prosperity of communities worldwide.