Freshwater fish species that undertake extensive migrations are facing a critical decline, with recent assessments revealing a staggering 81% drop in their populations over the past fifty years. A new report from the United Nations highlights the urgent need for conservation efforts to protect these vital species, which are integral to both ecosystems and the livelihoods of millions of people worldwide.
A Grim Assessment
The plight of migratory fish has largely been overlooked, but a comprehensive study encompassing over 15,000 species—a significant leap from just 3,000 in previous assessments—has brought their struggles to the forefront. The report identifies thirty flagship species, including the golden mahseer and goonch catfish, as priority targets for global conservation initiatives. Dr. Zeb Hogan, a biologist at the University of Nevada, Reno, and one of the report’s co-authors, emphasised the importance of these fish, stating, “Freshwater fish support hundreds of millions of people around the world.”
These species not only provide food for approximately 200 million individuals but also present immense biodiversity that needs safeguarding. Hogan illustrated the diversity of migratory fish, describing them as ranging from the massive piraíba catfish, which can weigh over 650 pounds, to the stunning golden dorado of South America and the tropical eels migrating vast distances across Oceania.
Pressing Threats
The decline of migratory fish populations can be attributed to a trifecta of threats: habitat destruction, pollution, and overfishing. Michele Thieme, deputy lead for freshwater at the World Wildlife Fund US and a contributor to the report, pointed out that habitat loss often results from the construction of dams that fragment river systems, thereby preventing fish from reaching their spawning grounds.
Dr. Janina Gray, head of science at the environmental charity WildFish, noted that in Europe, fish face an average of one barrier every kilometre, which significantly hampers their migration. These barriers, often outdated culverts or weirs, not only waste the fish’s energy but also increase their susceptibility to disease and predation. “The cumulative effect on migrating fish is enormous,” Gray warned, highlighting the dire need for action to remove these obstacles.
A Global Response Needed
To combat the alarming decline in migratory fish populations, coordinated international efforts are paramount. The Convention on the Conservation of Migratory Species, established in 1979, aims to unite countries in the protection of migrating species. The UN is advocating for the inclusion of the thirty identified fish species in the convention’s framework during its next annual meeting in three years.
Historically, conservation efforts have focused on more recognisable species, such as large mammals and marine animals, leaving freshwater fish underrepresented. However, as noted by Amy Fraenkel, the UN Executive Secretary for the Convention, it is now time for migratory freshwater fish to receive the attention they deserve. Success stories exist, such as the recovery of the saiga antelope, which benefitted from international conservation initiatives following a catastrophic population decline.
Why it Matters
The sharp decline in migratory fish populations signals a broader environmental crisis that could have severe repercussions for both ecosystems and human communities. Freshwater fish play a crucial role in maintaining healthy aquatic environments and supporting the livelihoods of millions. As we face growing challenges from climate change and human activity, the time for decisive action is now. Protecting these species is not just about preserving biodiversity; it is about safeguarding the future of our ecosystems and the communities that rely on them for survival. Without concerted global efforts, we risk losing not only the fish but also the intricate web of life that depends on them.
