The Migration Journey of a Sturgeon: A Call for Cross-Border Cooperation

© Hartmut Jungius / WWF

Sturgeon, among the oldest fish species on Earth, have been around for over 200 million years. These prehistoric giants can live for decades and reach impressive sizes, with some species growing up to six meters long. Now on the brink of extinction due to overfishing, a flourishing illegal caviar trade and habitat loss, sturgeon are categorized as the most endangered species groups worldwide.

In light of World Fish Migration Day, the environmental organization WWF has revealed a rare discovery, emphasizing the urgent need for cross-border collaboration in protecting migratory species. 

In February 2024, a Bulgarian fisherman, who has been collaborating with WWF for over eight years in monitoring the ancient species, had an unusual catch. He found a young Russian sturgeon that had traveled to Bulgaria's North Black Sea coast all the way from Turkey, providing evidence of previously undocumented migration pattern. "How the fish move in the Black Sea is still largely unknown. From a scientific point of view the Black Sea is essentially a black hole regarding sturgeon behavior—we have extremely limited information on their activities and movements there. Discovering a marked specimen that we can trace back to Turkey is an extremely uncommon and therefore valuable scientific observation,” said Beate Striebel, WWF Sturgeon Initiative Lead. 

The Challenges of Tracking Sturgeon Migrations
This sturgeon, about 30 cm long and weighing 297 grams, was identified as artificially bred, evident from its curved pectorals and a yellow T-bar tag. However, the tag itself was not enough to reveal the entire origin of this fish. Different countries tag fish with different techniques and numbers, but this information is not actively shared, centrally accessible, or updated regularly. This lack of coordination presents a significant obstacle. A sturgeon released in one country can easily show up in the monitoring or bycatch of another country—not only along the Black Sea but also in the connecting rivers. The success of such releases, which are costly and require experienced staff, and many years of dedicated work, cannot be evaluated well if information about releases and re-captures is not exchanged.

By a fortunate coincidence, the sturgeon experts from WWF had recently seen a similar tag at a fisheries conference in Turkey. This connection helped reveal that the sturgeon had been released just four months earlier, in October 2023, near the Turkish river Yeşilırmak, close to Samsun. The release was part of a restocking program by Türkiye's General Directorate of Fisheries and Aquaculture under the Ministry of Agriculture and Forestry. 

Migratory species need efforts beyond institutional projects and beyond country boundaries
The new Living Planet Index (LPI) report on freshwater migratory fishes, published just a few days ago, reveals a staggering 81% collapse in monitored population sizes on average between 1970 to 2020, including catastrophic declines of 75% in Europe. 

Habitat loss and degradation – including fragmentation of rivers by dams and conversion of wetlands for agriculture – account for half of the threats to migratory fishes, followed by over-exploitation. Increasing pollution and the impacts of climate change are also fueling the fall in freshwater migratory fish species, which have now been declining consistently for 30 years.

Migratory species need efforts beyond institutional projects and beyond country boundaries. They cross waters of several jurisdictions and will not pay attention to show up in the exact same monitoring efforts where they have been previously released. Experts in the Danube and the Black Sea have started to come together, but connections rely on personal relationships or are project bound. 

WWF urges enhanced cooperation among countries bordering the Black Sea and connected river systems. “A structured and ongoing exchange of information between experts, supported by governments and international bodies, is crucial,” added Beate Striebel. “On World Fish Migration Day, let's pledge to work together across borders to ensure the survival of these magnificent creatures, because only together can we make a difference.”