A stark warning has emerged regarding the dramatic decline of migratory fish species worldwide, with recent research revealing an alarming 81% decrease in their populations over the past fifty years. This decline is largely attributed to habitat destruction, pollution, and overfishing. In response, the United Nations has identified 30 key fish species requiring immediate conservation efforts, highlighting the critical role these fish play in both ecosystems and human livelihoods.
The State of Freshwater Fish
A comprehensive assessment conducted by an international team of scientists has illuminated the precarious status of migratory freshwater fish. These species, which account for roughly half of all fish globally, are essential for the sustenance of millions. Dr. Zeb Hogan, a biology professor at the University of Nevada, Reno, and co-author of the report, emphasised their importance: “Freshwater fish support hundreds of millions of people around the world, so for humans, they’re very important.” He noted the incredible diversity of these fish, which includes species that can weigh over 650 pounds and migrate thousands of miles.
The UN’s latest report marks a significant expansion of previous assessments, increasing the number of evaluated species from 3,000 in 2011 to over 15,000 today. This extensive review has enabled the identification of 325 fish species that need to be included in a global conservation agreement. Among these are 30 priority species, including the Allis Shad and the Atlantic Salmon, which are native to the UK.
Drivers of Decline: Overfishing and Habitat Loss
The report highlights two primary threats to migratory fish: overfishing and habitat degradation. Michelle Thiem, deputy lead for freshwater at the World Wildlife Fund US, pointed out that species like the golden mahseer, revered in the Himalayan region for its cultural significance, are facing existential threats due to these factors. “Habitat loss includes things like dams that fragment a river system, and can change the natural flow regime of a river,” she explained. Such changes hinder fish from accessing their spawning grounds, further exacerbating population declines.
The issue of disrupted migration is particularly acute in Europe, where it is estimated that fish encounter an obstruction every kilometre on average. Dr. Janina Gray, head of science at the environment charity WildFish, noted that even minor barriers, such as redundant weirs, can have a cumulative adverse effect on fish. “It can have a massive impact in terms of the energy reserves fish are using to get over the barriers,” she said, making them more vulnerable to disease and reducing their chances of successful spawning.
A Collaborative Approach to Conservation
The migratory patterns of these species often span national borders, necessitating coordinated conservation efforts among countries to enhance population recovery. The Convention on the Conservation of Migratory Species, a UN treaty established in 1979, aims to ensure that nations collaborate to protect migratory species across the globe. The UN is now advocating for the inclusion of the 30 identified fish species in the treaty during its next annual meeting, set for three years from now.
Historical precedents exist for successful conservation interventions, as demonstrated by the recovery of the saiga antelope, which benefitted from international efforts following a catastrophic population decline. Amy Fraenkel, the UN Executive Secretary for the Convention on Migratory Species, acknowledged the historical focus on more prominent species like big cats and whales, stating, “It is now the turn of migratory freshwater fish to benefit from coordinated action.”
Why it Matters
The decline of migratory fish populations signifies a critical failure in global biodiversity and ecosystem health. These species not only contribute to the ecological balance but also serve as a vital resource for millions of people who rely on them for food and cultural practices. Immediate and concerted action is essential to halt this decline and ensure the survival of these species, which are a testament to the intricate connections within our natural world. The proposed conservation measures by the UN could be pivotal in reversing the trends threatening these iconic fish, ultimately supporting the livelihoods and well-being of communities worldwide.
