Environment
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Study: Estonian Dams Fuel Parasite Epidemic in Trout Populations
A new study from the Estonian University of Life Sciences reveals that dams on the nation's rivers are warming water by an average of 4-5 degrees Celsius, creating breeding grounds for a parasite causing deadly kidney disease in vulnerable trout populations.
- —A new study by Estonian University of Life Sciences and Swedish University of Agricultural Sciences researchers reveals that dams on Estonian rivers significantly increase water temperatures downstream, creating conditions favorable for a parasite that causes a serious kidney disease in trout.
- —The study found that reservoirs act as solar collectors, warming river water by an average of 4-5 degrees Celsius in summer, which in turn promotes the proliferation of the parasite Tetracapsuloides bryosalmonae.
- —Trout living downstream of dams exhibited higher parasite loads and more severe symptoms of proliferative kidney disease (PKD) compared to those upstream, with young fish being particularly vulnerable.
- —Researchers suggest that alongside dam removal, measures like planting trees and shrubs along riverbanks to shade the water are crucial for restoring river ecosystems and mitigating the spread of the disease.
Recap
The research exposes a critical flaw in river restoration strategies that focus solely on fish migration. By demonstrating that dams create thermal pollution hotspots that cultivate disease, the study forces a policy re-evaluation. This is not a localized Estonian issue; it implies that thousands of dams across Europe may be creating similar ecological traps, undermining conservation efforts and threatening cold-water species on a continental scale.