Freshwater fish species that undertake extensive migrations are facing a crisis, with a staggering 81% decline in their populations over the past fifty years, according to a new report from the UN. This alarming trend is primarily driven by habitat destruction, pollution, and overfishing, threatening not only the biodiversity of aquatic ecosystems but also the livelihoods of millions who rely on these species for sustenance.
A Global Conservation Priority
The report highlights 30 key migratory fish species that require immediate global conservation efforts. Among these are the golden mahseer and the goonch catfish, both of which play vital ecological and cultural roles in their respective habitats. The findings are the result of an extensive assessment of over 15,000 freshwater fish species, which represent half of all fish on the planet. The data reveals that this often-overlooked group is not just a backdrop to our ecosystems, but essential to the livelihoods of hundreds of millions worldwide.
Dr. Zeb Hogan, a co-author of the report and a biology professor at the University of Nevada, Reno, stated, “Freshwater fish support hundreds of millions of people around the world, so for humans, they’re very important.” He emphasised that these species, which can vary dramatically in size and migratory capabilities, are critical for food security and ecological diversity.
The Threats They Face
The primary factors contributing to the decline of migratory fish are habitat loss and overfishing. Dams fragment river systems and disrupt natural flows, making it difficult for fish to reach their spawning grounds. Michele Thieme, deputy lead for freshwater at the World Wildlife Fund US, pointed out that iconic species like the golden mahseer, revered in Himalayan culture, are facing significant threats that extend beyond economic considerations. “Habitat loss includes things like dams that fragment a river system, and can change the natural flow regime of a river,” she explained.
The report also highlights the plight of the piraíba, or giant catfish, which has been recommended for urgent protection due to its declining numbers. Meanwhile, in the UK, species like the river lamprey have suffered drastically from pollution, a legacy of the industrial revolution that continues to impact aquatic ecosystems.
Barriers to Migration
In Europe, the situation is particularly dire, with migrating fish facing barriers every kilometre on average. These obstacles, often small and redundant, such as weirs and culverts, can have a profound cumulative effect on fish populations. Dr. Janina Gray, head of science at the charity WildFish, noted, “The energy reserves fish are using to get over the barriers make them more susceptible to disease and predation.” The impact is not just ecological; it threatens the very fabric of cultural and community practices tied to these species.
As many fish undertake migrations that span international borders, coordinated conservation efforts are essential. The UN is advocating for the inclusion of these 30 priority fish species in the Convention on the Conservation of Migratory Species, an international treaty established in 1979 aimed at fostering collaborative protection efforts.
A Model for Recovery
The success of international conservation initiatives is illustrated by the recovery of the saiga antelope, which, after a catastrophic decline, rebounded significantly thanks to concerted anti-poaching efforts. Amy Fraenkel, the UN Executive Secretary for the Convention on Migratory Species, expressed hope that the focus will now shift to migratory freshwater fish, which have long been overshadowed by more ‘charismatic’ species like big cats and marine mammals.
The UN plans to propose the addition of these fish species to the treaty at its upcoming annual meeting, signalling a pivotal moment in the fight for their survival.
Why it Matters
The decline of migratory fish species is not merely an environmental issue; it is a pressing humanitarian concern. These fish are integral to the diets and cultural practices of countless communities around the globe. Protecting them is crucial for maintaining biodiversity and ensuring food security for future generations. As the world becomes increasingly aware of the interconnectedness of ecosystems and human livelihoods, the urgency to act has never been clearer. The time for concerted action is now, as we strive to safeguard the future of these vital aquatic species.
