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Fish stocking as a fisheries compensation method in hydropower operations no longer meets latest legal and scientific requirements, according to a new study from the University of Eastern Finland. Published in Water International, the study focuses on ecological flows from the viewpoints of law and biology.
After the World Wars, the vast majority of Finnish rivers were harnessed for hydropower operations. Initially, the Finnish legislation included an obligation to build fishways as a method to compensate for hydropower harm to fisheries. However, fish farming rapidly replaced fishways as the primary compensatory action. Initially, fish stockings were ahead of their time and among the first examples of ecological compensation measures set for the industries. In the early days of their use, they also produced good catches in both commercial and recreational fisheries.
Research - Stocking - Cycles - Fish - Prior
However, research has since shown that fish stocking cannot permanently replace the natural reproductive cycles of migratory fish. Prior to the industrial revolution, Finland boasted 25 Atlantic salmon, 72 anadromous brown trout and dozens of inland rivers with landlocked salmonids. Yet currently, the number of Finnish rivers sustaining natural reproduction of salmon has been reduced to four, and only small and rare populations of wild migratory brown trout, migratory whitefish and migratory grayling have survived.
"New genetic studies have shown that fish farming alters the genetic traits of farmed fish. As fish adapt to the farm environment, their genetic traits change and they no longer survive in the wild as well as they used to," says Professor of Evolutionary Aquatic Biology Anssi Vainikka from the University of Eastern Finland.
Differentiation - Populations - Branches - River - Diversity
Genetic differentiation has been observed even among salmonid populations living in different branches of the same river. This genetic diversity, which is essential for, e.g., adaptation to climate change, cannot be maintained in fish farming.
The study concludes that the harm caused by hydropower operations...
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