SYDNEY, May 29 (Xinhua) -- Dams are causing significant harm to migratory river species, such as fish, eels, crustaceans and snails that rely on unbroken pathways between rivers and oceans to complete their life cycles, said a global study.
The research synthesized over 100 studies and is the first global analysis of how dam-induced river fragmentation affects these so-called diadromous species, Australia's University of Tasmania said in a news release on Wednesday.
The findings highlight a sharp decline in species abundance, diversity, and genetic health due to blocked migration routes and disrupted habitats, said researchers, including University of Tasmania freshwater animal ecologist Liew Jia Huan and the study's lead author Jeffrey Chan from the University of Hong Kong.
While fish passes or "fish ladders" are widely used to mitigate these effects, the study found they often fail, especially when not tailored to the local species' behavior.
"The impacts of dams were the harshest on species that cannot survive in isolated, landlocked environments, and fish with limited climbing abilities, unlike better climbers such as eels," Liew said.
The researchers identified dam removal as the most effective method to restore ecological connectivity, though it can be expensive and socially complex.
As global dam construction accelerates, driven by energy and water demands, the study, published in Biological Reviews, urges more rigorous environmental assessments before development begins, and calls for greater research into understudied tropical regions and lesser-known migratory species like snails and crabs. Enditem
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