In a striking revelation, a recent UN report highlights the alarming decline of migratory fish populations, with an estimated 81% drop over the past fifty years. This decline is largely driven by the dual threats of habitat destruction and overfishing, putting immense pressure on these vital species. The report identifies thirty key fish, including the golden mahseer and the goonch catfish, as priorities for global conservation efforts.
The Magnitude of the Crisis
Migratory fish, which traverse vast distances through rivers, lakes, and coastal waters, are essential to the health of aquatic ecosystems and the livelihoods of millions. According to a team of international scientists, these fish represent half of all fish species worldwide. Their critical role in food security is underscored by Dr. Zeb Hogan, co-author of the report and a biology professor at the University of Nevada, Reno. He notes that these species provide sustenance for approximately 200 million people globally, while also showcasing an extraordinary diversity that merits protection.
Dr. Hogan’s words resonate with urgency: “You have fish that can get over 650 lb (295 kg) that can migrate over 7,000 miles. Every shape and size of animal you can imagine… these beautiful golden dorado that make long-distance migrations in South America, tropical eels that are moving thousands of miles in Oceania.”
Key Species at Risk
The report marks a significant expansion of research on freshwater migratory fish since the UN’s initial assessment in 2011, which only examined 3,000 species. This latest evaluation encompasses over 15,000 species, identifying 325 fish that require immediate monitoring and protection under a global conservation agreement. Among these, 30 fish species have been highlighted as priorities, including several native to the UK, such as the Allis shad, River lamprey, Brook lamprey, and Atlantic salmon.
Michele Thieme, deputy lead for freshwater at the World Wildlife Fund US and a contributor to the report, emphasises the cultural significance of these species. She points out that the golden mahseer, an iconic fish in the Himalayas, is not only an economic asset but also holds deep cultural and spiritual value for local communities. However, both overfishing and habitat degradation threaten these crucial populations.
Barriers to Migration
One of the most pressing challenges facing migratory fish is the fragmentation of their habitats due to dams and pollution. Thieme explains, “Habitat loss includes things like dams that fragment a river system, and can change the natural flow regime of a river, which results in fish not being able to connect to their spawning habitats.”
This problem is particularly acute in Europe, where migratory fish encounter barriers every kilometre on average. Dr. Janina Gray, head of science at environmental charity WildFish, highlights the cumulative impact of these obstacles. The energy expenditure required for fish to navigate these barriers can lead to increased susceptibility to disease and predation, ultimately hindering their spawning success.
A Call to Action
The report urges coordinated international efforts to safeguard these migratory fish, which often cross national borders during their journeys. Prof. Hogan stresses the importance of collaboration among governments to mitigate the threats these species face. The Convention on the Conservation of Migratory Species (CMS), a UN treaty established in 1979, serves as a framework for such cooperation.
The UN plans to propose the addition of the 30 identified fish species to the CMS during its annual meeting in three years’ time, a move that could dramatically enhance conservation efforts. Historical precedents, such as the recovery of the saiga antelope following international conservation initiatives, offer hope that similar successes can be achieved for migratory fish.
Why it Matters
The decline of migratory fish populations represents more than just an environmental issue; it is a profound threat to global biodiversity, food security, and cultural heritage. As these species vanish, so too do the ecosystems they inhabit and the livelihoods they support. Urgent action is needed to reverse this trend and ensure that future generations can experience the rich diversity of life that migratory fish bring to our planet. The call for their protection resonates not just within scientific communities but across cultures and economies worldwide, reminding us that the health of our ecosystems is intrinsically linked to our own survival and well-being.
