A new study has revealed that freshwater fish populations have declined by more than 80% since 1970.
Global Decline
The study found that freshwater fish populations are declining in all regions globally, with the most severe declines occurring in South America and the Caribbean, where populations have plummeted by 91% over the past 50 years. This region hosts the world's greatest density of freshwater fish migrations, but dam construction, mining, and water diversion are devastating river ecosystems. In Europe, freshwater fish populations have declined by 75%, according to the Living Planet Index (LPI).
Threatened Species
Meanwhile, the International Union for Conservation of Nature (IUCN) reports that 25% of freshwater fish species are threatened with extinction, with migratory species facing greater threats. These figures exclude changes in Africa, but researchers believe many species there are facing similar stressors.
Causes of Decline
Freshwater fish migrate either partially or entirely within freshwater systems, with some species born in the ocean and migrating to freshwater, or vice versa. They are a vital part of the diet and livelihoods of millions of people worldwide. However, many rivers no longer flow freely due to dams and other barriers that block fish migration. Other threats include pollution from urban wastewater, industrial discharge, and runoff from roads and farms. Climate change is also altering habitats and affecting freshwater systems. Unsustainable fishing practices pose another threat.
Call to Action
"The catastrophic decline of migratory fish populations is a wake-up call for the world," said Herman Wanningen, founder of the World Fish Migration Foundation (WFMF), a contributing partner to the study. "We must take urgent, global action now to save these species and the rivers they depend on." The study's authors call for river restoration and protection, and the removal of barriers to fish migration. They also urge the exploration of renewable energy alternatives to the thousands of new hydropower dam projects planned worldwide. Last year, a record 487 barriers were removed in 15 European countries.
Importance of Understanding Marine Impacts
"As many migratory fish species spend a large proportion of their lives at sea, a better understanding of the impacts on both their marine and freshwater habitats is essential for effective management," said Dr. Anthony Acou of the French National Institute for Agricultural, Food, and Environmental Research (INRAE).
Summary
Freshwater fish populations have experienced a dramatic decline of over 80% since 1970. Multiple factors, including dam construction, pollution, and climate change, are driving this decline. To protect these species and the ecosystems they support, global action is needed to restore rivers, remove barriers to fish migration, and explore sustainable energy alternatives.