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Decline in Migratory Freshwater Fish Threatens Ecosystems, Livelihoods

From 1970 to 2020, migratory freshwater fish populations declined by 81%, with significant drops in Europe (75%) and Latin America and the Caribbean (91%), according to a study.

By Ground report
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Alarming decline in migratory freshwater fish populations: study

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A report raises concerns about the rapid decline of migratory freshwater fish populations, including iconic species like salmon, trout, eels, and sturgeon. These creatures, which undertake long migrations at different life stages, are vital for maintaining freshwater ecosystems and ensuring food security for millions.

The latest Living Planet Index 2024 update on migratory freshwater fish revealed an 80% decline in their populations since 1970, averaging 3.3% annually, threatening their existence.

From 1970 to 2020, migratory freshwater fish populations declined by 81%, with significant drops in Europe (75%) and Latin America and the Caribbean (91%), according to a study. The study suggests conservation efforts could help.

Research by the World Fish Migration Foundation, Zoological Society of London (ZSL), the International Union for Conservation of Nature (IUCN), The Nature Conservancy (TNC), Wetlands International Europe, and the NGO WWF is part of the World Fish Migration Day on May 25.

Migratory fish populations have fallen 81% since 1970

The new Living Planet Index (LPI) report on migratory freshwater fish reveals catastrophic declines of 91% in Latin America and the Caribbean and 75% in Europe between 1970 and 2020. This continued loss endangers food security and livelihoods, especially in vulnerable communities in Latin America, Africa, and Asia, the survival of other species, and the health and resilience of rivers, lakes, and wetlands.

The report shows that migratory fish populations are declining worldwide, especially in South America and the Caribbean, where a 91 percent decline has been recorded over the past 50 years. This region hosts the world's largest freshwater migration, but human activities like dam construction, mining, and stream diversion projects are damaging the ecosystem and contributing to the decline.

Europe's migratory freshwater fish populations dropped by 75%, North America's by 35%, and Asia and Oceania's by 28%. The lack of African data makes it hard to assess the situation there.

"The catastrophic decline in migratory fish populations is a wake-up call. We must act now to save these keystone species and their rivers," said Herman Wanningen, founder of the World Fish Migration Foundation. "Migratory fish are central to Indigenous Peoples' cultures, nourish millions, and sustain a vast web of species and ecosystems. We cannot let them slip away."

Habitat loss and degradation account for half of the threats to migratory fish, including river fragmentation by dams and wetland conversion for agriculture, followed by overexploitation. Increased pollution and climate change worsen the population decline.

"The catastrophic decline in migratory fish populations is a wake-up call," and urged immediate action to save these key species and their rivers.

Conservation efforts boosted one-third

However, the study notes that nearly a third of the species have increased due to conservation efforts, improved management, habitat restoration, barrier removal, creation of sanctuaries, and legal protection.

“Popular action to reconnect European rivers and improve fish mobility is increasing,” said Wetlands International Europe director, Chris Baker, who explained that together with Wetlands International, the Trans-European Waterways Network “is helping to identify and prioritize the most important rivers and species to pay attention to.”

For this to reach a larger scale, “European governments must commit to and implement the Nature Restoration Act to help accelerate the recovery of our rivers and migratory fish,” says Baker.

Europe, US removing river barriers

Removal of dams, dikes, and other river barriers has increased in Europe in recent decades. In 2023, 487 barriers were removed, a 50% increase from the previous year. This practice has also increased in the United States.

"These migratory fish depend on freshwater streams and rivers for survival, and some make incredible journeys, traveling from small streams to large rivers, sometimes crossing entire continents to return to their birthplace," said Dr. Anjali Singh, a wildlife conservationist at the World Wide Fund for Nature (WWF).

The European eel can travel up to 10,000 kilometers (6,214 miles) in two years to reach its breeding ground near the Bahamas, highlighting the remarkable feats these creatures undertake.

The report identifies factors responsible for the decline, including disruption of migration routes due to human-made obstacles like dams, changing climate patterns, pollution, habitat destruction, and overexploitation.

"These migratory species face man-made obstacles and dangers during their journey," said Dr. Singh. "Changing climate and pollution bring new challenges."

During their migrations, fish need rest and food, but the destruction of natural habitats has made it harder for them to find sustenance, leading to fatigue and hunger, and potential death.

One-third of freshwater species are at risk of extinction, with migratory fish being especially vulnerable. Unimpeded flow of streams and rivers is crucial for their migration, but dams, city and industrial pollution, pesticide runoff from farms, and climate-induced water changes are threatening these species.

Researchers stress the need for sustainable renewable alternatives to the thousands of new hydroelectric dams worldwide and other measures to meet the Kunming-Montreal Global Biodiversity Framework's objectives of protecting 30% of continental waters and restoring 30% of degraded continental waters.

Achieving the Freshwater Challenge goal of restoring 300,000 kilometres of degraded rivers could reverse the trend of migratory fish population decline.

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