A new report by a coalition of global scientists highlights a dire situation facing migratory fish populations worldwide, revealing a staggering 81% decline over the past fifty years. This alarming trend is attributed to a combination of overfishing, pollution, and habitat destruction, particularly from dams that obstruct natural migratory routes. The United Nations has now prioritised thirty flagship species for conservation efforts, underscoring the critical need to protect these aquatic ambassadors of biodiversity.
The State of Freshwater Fish
Migratory fish are a vital component of our ecosystems, yet they remain underappreciated. A recent comprehensive assessment of over 15,000 freshwater fish species shows that their populations are in freefall. This group makes up half of all fish species but has been largely overlooked in conservation dialogues. Dr. Zeb Hogan, a prominent biologist and co-author of the report, points out the crucial role these fish play in sustaining the livelihoods of millions: “Freshwater fish support hundreds of millions of people around the world, so for humans, they’re very important.”
Among the species highlighted for urgent protection are the golden mahseer and the piraíba, also known as the giant catfish. These fish are not just vital for food security; their remarkable migratory journeys—sometimes spanning thousands of miles—demonstrate the intricate connections within our natural world. Dr. Hogan emphasises the need for awareness: “You have fish that can get over 650 lb (295kg) 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.”
The Threats They Face
The threats to migratory fish are multifaceted. Overfishing and habitat loss are the primary culprits, with rivers being fragmented by dams that disrupt their natural flow. Michele Thieme, deputy lead for freshwater at the World Wildlife Fund US and a contributor to the report, 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.”
In Europe, the situation is particularly grave, as fish encounter barriers every kilometre (approximately 0.6 miles) on average, significantly hindering their migratory routes. Dr. Janina Gray, head of science at environment charity WildFish, warns of the cumulative effects: “It can have a massive impact in terms of the energy reserves fish are using to get over the barriers. That makes them more susceptible to disease and predation, and they will spawn in suboptimal grounds.”
A Global Conservation Effort
Recognising the need for concerted action, the UN is advocating for the inclusion of these thirty priority fish species in the Convention on the Conservation of Migratory Species. This treaty, established in 1979, aims to foster international cooperation for the protection of migratory species across borders. The UN’s proposal will be discussed at the convention’s annual meeting in three years, marking a pivotal opportunity for the future of these fish.
The Saiga antelope serves as a beacon of hope for successful conservation. After experiencing a catastrophic decline in 2015, international efforts have led to a remarkable rebound, with populations now exceeding one million. Amy Fraenkel, the UN Executive Secretary for the Convention on Migratory Species, asserts that it is now time for migratory freshwater fish to receive similar attention: “The focus has clearly been on some of the more well-known, more visible species. It’s now the turn of migratory freshwater fish to benefit from coordinated action.”
Why it Matters
The plight of migratory fish is not just an environmental issue; it is a matter of human survival and cultural identity for countless communities worldwide. These fish are integral to ecosystems and local economies, and their decline poses a significant threat to food security and biodiversity. If we fail to act, we risk losing not only these majestic creatures but also the intricate ecosystems they support and the livelihoods of millions who depend on them. The urgent call for protection is not merely a plea for conservation; it is a rallying cry for our planet’s future.
