A stark warning has been issued about the drastic decline of migratory fish species, with new findings revealing an alarming 81% reduction in their populations over the past fifty years. This decline is linked to a combination of dam construction, pollution, and rampant overfishing that obstruct these vital species from reaching their breeding grounds. The United Nations has now identified 30 flagship fish species, including the golden mahseer and goonch catfish, for immediate conservation efforts.
A Comprehensive Assessment
In a significant study, international scientists evaluated over 15,000 species of freshwater migratory fish—representing half of all fish species worldwide. This assessment, an update from a 2011 report which only reviewed 3,000 species, highlights the urgent need for protection of these aquatic populations. Dr. Zeb Hogan, a professor of biology at the University of Nevada, Reno, and co-author of the report, emphasised that freshwater fish play a critical role in supporting the livelihoods of millions, providing sustenance for approximately 200 million people globally.
Hogan noted the extraordinary diversity of these fish, with some capable of migrating thousands of miles. “You have fish that can get over 650 lb (295kg) that can migrate over 7,000 miles,” he explained, referencing the majestic golden dorado and tropical eels that traverse vast distances in their natural habitats.
Threats to Survival
The report outlines the dire threats facing migratory fish, primarily overfishing and habitat destruction. Michele Thieme, deputy lead for freshwater at the World Wildlife Fund (WWF) US, highlighted the cultural significance of species like the golden mahseer, often referred to as the “tiger of the river.” This iconic fish faces challenges not just from overexploitation but also from the loss of its natural habitat due to human activity, including infrastructure development that disrupts river ecosystems.
Thieme pointed out that dams particularly fragment river systems, altering the natural flow and making it increasingly difficult for fish to access their spawning grounds. Furthermore, pollution has had a devastating impact, with species such as the river lamprey in the UK experiencing significant population declines since the industrial revolution.
Barriers to Migration
The problem of migration disruption is especially acute in Europe, where fish encounter barriers—such as weirs and culverts—every kilometre on average. Dr. Janina Gray, head of science at WildFish, noted that even small barriers can have a cumulative effect that drains energy from migrating fish, making them more vulnerable to disease, predation, and poor spawning conditions.
To address these challenges, coordinated international efforts are essential. Many migratory species traverse national borders, necessitating collaboration between governments to tackle the threats they face and facilitate the recovery of their populations.
A Path Forward
The UN is poised to propose that the 30 identified fish species be included in the Convention on the Conservation of Migratory Species during its upcoming annual meeting in three years. This treaty, established in 1979, aims to foster international cooperation to protect migratory species globally.
Success stories do exist, such as the recovery of the saiga antelope, which rebounded from a near-extinction crisis through concerted international anti-poaching efforts. Amy Fraenkel, the Executive Secretary for the Convention on Migratory Species, underscored the need for similar attention to be directed towards migratory freshwater fish, which have often been overlooked in conservation discussions.
Why it Matters
The decline of migratory fish species signals a broader environmental crisis that affects ecosystems, economies, and communities reliant on these fish for sustenance and cultural practices. Protecting these species is not only essential for biodiversity but also for the health of the planet. Without immediate action, we risk losing not only these remarkable fish but also the invaluable roles they play in the world’s freshwater ecosystems. The time has come for the global community to unite in safeguarding the future of our migratory fish.
