Rivers and the life they support provide many services: water supply, irrigation, navigation, hydropower, recreation and more. And migratory fish—like salmon, trout, dourada, shad, lamprey, giant catfish, sturgeon and eel—are a source of protein and for millions of people around the world.
In China, rapid development is affecting the Chinese sturgeon, one of the four indicator species WWF is watching as a sign of the Yangtze River’s overall health.
Migratory fish contribute to the food chain in different parts of the river, lake and marine ecosystems by moving nutrients and energy around these networks. Because they need a healthy river to survive, these fish are important indicators of a river’s health. Given the Yangtze is the only river in which the Chinese Sturgeon still swims, it is an important indicator of how we, collectively, are caring for China’s “Mother River.”
Challenges En Route
Barriers such as weirs (low walls built across streams), dams and sluices (a passage built for water to flow through with a gate for controlling water flow) for water management, hydropower and land drainage block river systems and physically prevent fish migrations. When fish migration is blocked, it often impacts the species reproduction and feeding patterns, depletes populations, damages rivers and nearby marine habitats, and allows non-native species to establish themselves in these changed conditions. These factors can have a detrimental effect on the livelihoods, culture, and quality of life of millions of people globally.
But blocking migration routes isn’t the only challenge these fish face. Dams and other barriers can change how rivers flow and the water temperature, both of which are essential for spawning.
Keep Fish Swimming
How can we save migratory fish like the Chinese Sturgeon? Simply put, it’s no different than the strategies we employ with other endangered species like tigers, elephants, and rhinos. We need to:
- protect the individuals that currently exist;
- grow the population through captive breeding;
- release offspring into the wild;
- protect the current habitat so they can survive;
- and provide the means for connectivity between spawning and rearing habitats.
WWF is working with conservationists, water and resource managers, dam developers and others are working together to restore and improve migration routes for fishes between and within rivers, deltas and the oceans. These ‘fishways’ are vital to their survival, and are increasingly part of barrier planning and development and management, alongside flow release. To improve rivers that house migratory fish, we can increase the amount, timing and duration of flows from barriers in order to better support the entire life cycle of fish, especially during spawning and early development.
While these strategies are proven mitigation strategies, the best intervention would be to maintain natural, free-flowing river networks all around the world. This requires proper planning at the basin level, which better protects overall river health, the ecosystem services that rivers provide, and migratory fish species.