As migratory fish species face unprecedented threats, urgent action is needed to prevent further declines in their populations. A recent UN report reveals that these vital aquatic creatures, which undertake extensive migrations through rivers and lakes, have seen a staggering 81% reduction in numbers over the past fifty years. Factors such as dam construction, pollution, and overfishing are jeopardising their ability to reach crucial breeding grounds, putting both ecosystems and human livelihoods at risk.
Shocking Declines in Freshwater Fish Populations
The report, compiled by a team of international scientists, evaluated more than 15,000 freshwater migratory fish species—representing half of the world’s fish diversity. Among the species highlighted for immediate conservation attention are the golden mahseer and the goonch catfish, both of which are emblematic of broader ecological challenges. Dr. Zeb Hogan, a co-author of the study and a professor of biology at the University of Nevada, Reno, emphasised the significance of these fish, stating, “Freshwater fish support hundreds of millions of people around the world, so for humans, they are very important.”
With migratory freshwater fish providing sustenance for approximately 200 million people globally, their plight cannot be ignored. Hogan further illustrated the diversity of these species, mentioning remarkable examples such as enormous fish that can weigh over 650 pounds and migrate thousands of miles.
Habitat Loss and Overfishing Threaten Iconic Species
The UN’s previous assessment of migratory fish in 2011 saw only 3,000 species evaluated. This new report expands that scope significantly, identifying 325 species requiring monitoring and protection under a global conservation agreement. Of these, 30 species have been prioritised, including several that are found in the UK, such as the Allis Shad, River Lamprey, Brook Lamprey, and Atlantic Salmon.
Many of these fish face dual threats from overfishing and habitat degradation. Michele Thieme, deputy lead for freshwater conservation at the World Wildlife Fund US and a contributor to the report, highlighted the cultural significance of species like the golden mahseer, revered in the Himalayas for both economic and spiritual reasons. However, she warned that habitat destruction—exacerbated by dams disrupting river systems—hinders their access to spawning grounds.
The river lamprey, known for its unique jawless structure, has experienced severe declines in the UK largely due to pollution stemming from industrial activities. These threats are compounded by the proliferation of barriers like weirs and culverts, which obstruct migratory routes and significantly undermine the resilience of fish populations.
International Cooperation is Crucial
Migration routes often span multiple national borders, necessitating coordinated efforts among governments to effectively address the challenges these species face. Prof. Hogan pointed out the importance of international collaboration, stating that the Convention on the Conservation of Migratory Species, a UN treaty established in 1979, serves as a vital framework for protecting migratory wildlife.
The UN is advocating for the addition of the identified 30 fish species to this treaty at its forthcoming annual meeting in three years. This move represents a hopeful step towards ensuring these fish receive the protection they urgently require.
Success stories from other species, such as the saiga antelope, demonstrate the potential for recovery following dedicated conservation initiatives. After suffering a catastrophic decline, the saiga’s population has rebounded thanks to international anti-poaching efforts. This precedent offers optimism that similar strategies could be successful for migratory fish.
Why it Matters
The decline of migratory fish species is not merely a conservation issue; it strikes at the heart of food security and ecological balance. These species are integral to the livelihoods of millions, and their loss could have cascading effects on ecosystems and communities alike. As the world grapples with the dual crises of biodiversity loss and climate change, the need for swift and decisive action to protect migratory fish has never been more pressing. The health of our rivers and lakes—and by extension, the wellbeing of countless people—depends on the success of these conservation efforts.
