Migratory Fish Population Down By 80% Since 1970, Fastest In South America And Caribbean

Migratory fish populations, including salmon, trout, eel, and sturgeon have dropped by more than 80% since 1970.

Deafening Wake-Up Call

The study examines 284 freshwater fish species' population trends. Researchers pointed out that although there was little evidence, there might have been significant drops before 1970.

All across the world, populations are dropping, but in South America and the Caribbean, where the abundance of these species has decreased by 91% in the last 50 years, this decline is occurring at the quickest rate.

The greatest freshwater migrations in the world occur in this region, yet river ecosystems are being destroyed by dams, mining, and human water diversion. In Europe, migratory freshwater fish populations have decreased by 75%, as per the most recent update to the Living Planet Index.

Researchers noted that many species in Africa encountered several stresses, but there was not enough data to quantify population fluctuations in that region.

Some migratory freshwater fish are born at sea and migrate back into freshwater, or they are partially or completely dependent on freshwater environments. In certain instances, they have the ability to swim across entire continents before returning to their birthstream.

"The catastrophic decline in migratory fish populations is a deafening wake-up call for the world. We must act now to save these keystone species and their rivers," said Herman Wanningen, founder of the World Fish Migration Foundation, one of the organisations involved in the study.

The loss and degradation of habitat, which includes the division of rivers by dams and other obstacles and the conversion of wetlands for agricultural purposes, pose the greatest threat to migratory fish populations, with overexploitation coming in second.

In addition to providing food for millions of people worldwide and supporting a huge network of species and habitats, migratory fish are essential to the cultures of many Indigenous peoples.

The International Union for Conservation of Nature (IUCN) estimates that 25% of freshwater fish species face extinction, with migratory fish being disproportionately affected.

Previous studies have discovered comparable "catastrophic" decreases. The most recent report's authors demand improved long-term monitoring, the restoration and protection of waterways, and the elimination of impediments to migration.

Conservation Effort Benefits

There is some good news in the report.

The number of monitored species has increased by nearly one-third, indicating the potential benefits of conservation efforts and better management. Promising tactics encompass enhanced and/or species-specific fisheries management, habitat restoration, dam removal, establishment of conservation sanctuaries, and legal safeguarding.

For instance, thousands of dams, levees, weirs, and other river obstacles have been eliminated in Europe and the US in recent decades, and support for similar acts is growing. Europe eliminated a record 487 barriers in 2023, a staggering 50% more than the previous peak noted in 2022.

Meanwhile, along the Klamath River in California and Oregon, the biggest dam reductions in American history are currently taking place. Dam removals can be cost-effective, job-producing solutions that help reverse the worrying trend of biodiversity loss in freshwater systems as well as solutions that increase river health and resilience for people, too

In addition to safeguarding and rehabilitating healthy rivers, there is an immediate need to bolster monitoring programs, gain deeper insights into the life-history, migration, and behavior of fish species, broaden international collaboration by including more freshwater migratory fish species in the Convention on Migratory Species (CMS), and encourage increased public and political involvement.