Global Swimways: conserving migratory fish populations

Migratory bird populations have long been supported through conservation schemes protecting their flight paths (which often span across continents and oceans). The mapping of such ‘flyways’ – used by millions of birds – allows for habitats at key stop-off points to be conserved and restored through protected area designations such as Ramsar wetland sites. Migratory bird flyways circle the world, and so protecting such key sites – variously used for feeding, breeding and over-wintering by different species – are crucial is crucial for the conservation of migratory bird populations on a global scale.

The term ‘flyway’ was coined by the American biologist Frederick Lincoln 1935 in an effort to describe migratory birds’ ‘ancestral routes’ of movement across seasons. The concept has been since been widely taken up in bird conservation – it’s a key idea in BirdLife International’s protected area planning, for example. Advances in tracking technologies are increasingly allowing scientists to understand not only to map and protect bird ‘flyways’, but also to observe how they are changing in response to pressures such as climate change, urbanisation and deforestation.

In comparison, the conservation of global migratory freshwater fish populations is lacking. Migratory fish species may travel thousands of miles between their spawning and feeding grounds, often moving between marine and freshwater habitats. The health of migratory fish populations therefore requires healthy, connected ecosystems which span both biogeographical and political boundaries. Many migratory fish species are important in sustaining human livelihoods, whilst others – such as the Atlantic salmon and Beluga sturgeon – are cultural icons which may act as ‘flagships’ for the conservation of wider ecosystems.

However, migratory fish species are in decline across the world as a result of multiple human pressures. Dam and weir construction can block migratory routes up river systems, water abstraction and pollution can destroy spawning grounds, whilst changing water temperatures as a result of climate change can alter food availability for migratory species. At present, though, too little is known about the status of many global migratory fish species and their conservation needs.

In response, a new ‘Global Swimways’ project has been launched this month, aiming to apply the insights of the ‘flyway’ concept to global migratory fish conservation. As part of this project, scientists will create the first global map of fish migration routes, identifying migration hotspots or ‘swimways’ and develop a new tool that highlights presence of migration routes near existing or planned infrastructure.

“Since the 1930s, people have developed and utilised the concept of flyways for the conservation of birds. They realised that in a world of changing habitats and building threats, you need global cooperation. It has led to successful agreements such as the Ramsar convention and international policies for conservation of ecological hotspots,” says Dr. William Darwall, project lead of the Global Swimways project, and Head of the Freshwater Biodiversity Unit of IUCNs Global Species Programme.

“We believe we can similarly use this developing concept of swimways for migratory fish and aim, through this project, to gain the momentum for taking this forwards as a tool to inform global policy and raise awareness leading to action. As soon as we have increased our knowledge and understanding of individual species migration routes, we will set criteria to identify swimways as globally important migration corridors.”

The project is a partnership between IUCN, the UN Environment Programme World Conservation Monitoring Centre, the University of Cambridge and the World Fish Migration Foundation. It is intended that the ‘swimways’ concept will help strengthen arguments for the conservation of migratory fish with policy makers. The project aims to raise awareness of the economic and cultural value of migratory fish, alongside their vulnerabilities to development along migration routes.

It is intended that the project will help inform the cost-benefit analyses made in planning large-scale dams and hydropower constructions (which are booming across the world). In other words, the Global Swimways project intends to highlight the value of global migratory fish and their remarkable life-cycles in an effort to strengthen their conservation and restoration.

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Find out more about the ‘Global Swimways’ project here.

Explore the ‘Swimways of the World’ map produced for World Fish Migration Day.