Migratory freshwater fish populations 'down by more than 80% since 1970' 

Many rivers are no longer flowing freely due to the construction of dams and other barriers, which block species’ migrations. There are an estimated 1.2 million barriers across European rivers.

Migratory fish populations, which form the basis for diets and livelihoods globally, have crashed by more than 80% since 1970, new findings show.

Populations are declining in all regions of the world, but it is happening fastest in South America and the Caribbean, where abundance of these species has dropped by 91% over the past 50 years.