• Globally, monitored populations of migratory freshwater fish have declined by an average of 76%* between 1970 and 2016.
• Monitored sturgeon populations have declined by an average of 91%.

Populations of migratory freshwater fish species have plummeted by 93% on average in Europe, since 1970. No surprise considering the rise of hydropower, overfishing, climate change and pollution, all drivers of population decline linked to human use and impact. These are the findings of the first comprehensive global report on the status of freshwater migratory fish, issued today by the World Fish Migration Foundation and ZSL (Zoological Society of London).

Arjan Berkhuysen, Managing Director of the World Fish Migration Foundation says, “Catastrophic losses in migratory fish populations show we cannot continue destroying our rivers. This will have immense consequences for people and nature across the globe. We can and need to act now before these keystone species are lost for good.”

Migratory fish, such as salmon and trout are vital to meet the food security needs, as well as support the livelihoods of millions of people around the world. They also play a critical role in keeping our rivers, lakes and wetlands healthy by supporting a complex food web. In Europe, some of the most vulnerable are mega-fishes such as Beluga sturgeon (Huso huso), which have shaped communities and livelyhoods along the Danube River for hundreds of years.

Sturgeons are considered to be ‘megafauna’ species, as they have a slow growth rate and therefore tend to reproduce at a later stage in life. For this reason, they cannot adapt quickly to changes in the environment, which makes them particularly susceptible to threats (Ripple et al. 2019). Moreover, as sturgeons are anadromous, i.e. they spawn upstream and feed in river deltas, they are vulnerable to any alteration of the river flow such as dam construction that might block their migratory routes to spawning and feeding grounds (Carrizo et al. 2017; He et al. 2017).

The International Union for the Conservation of Nature (IUCN) warns that 21 of the 25 species of sturgeon are threatened, with 16 classified as Critically Endangered, 2 as Endangered and 3 as Vulnerable (IUCN 2020). According to the LPI for migratory freshwater fish, monitored sturgeon populations have declined by 91% on average between 1970 and 2016. The report also reveals that the vast majority either do not have any information recorded as to whether there are known threats to the population (47%) or have known threats (53%).

WWF is working to restore the ecological aquatic corridors for migratory fish species in the Danube basin. Thus, through the MEASURES project we are developing and testing a methodology for mapping migratory fish habitats, a first step towards restoring ecological corridors, and we are also developping a strategy, with broad participation and acceptance of stakeholders, to maintain or restore functional corridors. We are also carrying out sturgeon restocking activities - 8000 younglings have been released so far in the Danube, in Romania and Hungary.

Habitat degradation, alteration, and loss account for approximately half of the threats to migratory fish. Wetlands are essential habitats for migratory fish species, but, globally, wetlands are disappearing three times faster than forests [1], while dams and other river barriers block fish from reaching their mating or feeding grounds and disrupt their life cycles.

“Migratory fish provide food and livelihoods for millions of people but this is seldom factored into development decisions. Instead, their importance to economies and ecosystems continues to be overlooked and undervalued – and their populations continue to collapse,” said Stuart Orr, WWF Global Freshwater Lead. “The world needs to implement an Emergency Recovery Plan that will reverse the loss of migratory fish and all freshwater biodiversity – for the benefit of people and nature.”

There is still an opportunity to turn the tide through more research to understand the fate of freshwater migratory fish and by developing practical solutions that restore and protect these animals. The authors and organizations associated with this report all call upon the global community to protect free-flowing rivers and guide basin-wide planning by addressing existing threats, adhering to ongoing conservation initiatives and water protection laws, investing in sustainable renewable alternatives to the thousands of new hydropower dams that are planned across the world and fostering public and political will.

References

 [1] Gardner, R., Finlayson, C. (2018) Global Wetland Outlook: State of the World’s Wetlands and their Services to People. The Ramsar Convention Secretariat: Gland, Switzerland.

*The average figure was found using abundance information for 1,406 populations of 247 fish species listed on the Global Register of Migratory Species as using freshwater for some of their migration.

Notes

More information about the Living Planet Index: The report findings were calculated using the Living Planet Database (LPD, LPI 2020). The authors extracted abundance information for 1,406 populations of 247 fish species listed on the Global Register of Migratory Species (GROMS; Riede 2001) as anadromous, catadromous, diadromous, amphidromous and potamodromous. Further work and research are needed on the global status and trends of migratory fish, especially given their economic, environmental, cultural, and recreational importance around the world. Additionally, more research and trials on effective management strategies are needed to protect populations around the globe. The collaborators on this report hope that these findings will encourage countries to prioritize freshwater protections and effective management strategies. 

ZSL (Zoological Society of London) is an international conservation charity working to create a world where wildlife thrives. From investigating the health threats facing animals to helping people and wildlife live alongside each other, ZSL is committed to bringing wildlife back from the brink of extinction. Our work is realised through our ground-breaking science, our field conservation around the world and engaging millions of people through our two zoos, ZSL London Zoo and ZSL Whipsnade Zoo. For more information, visit www.zsl.org

Founded in 2014, the World Fish Migration Foundation (WFMF) is an international organization with a mission to save migratory fish in rivers. The Foundation harnesses global attention for the challenges migratory fish face through a multitude of international, collaborative projects aimed at advocating for obsolete dam removals, and supporting initiatives that open up important swimways. For more information, visit www.worldfishmigrationfoundation.com

Photo © Jiri Bohdal