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Important wild freshwater fish species are under threat from humans in European seas, rivers and lakes. The Atlantic salmon, European eel and sturgeon are all migratory species that have seen massive population declines in the latter part of the 20th century, with the phenomenon continuing despite significant restocking of fish into the wild. For example, it is estimated that today’s eel population is down to only a fraction of what it was in the 1980s, with salmon facing a similar situation. Sturgeon, once a common fish, have disappeared in many countries and are considered the most threatened of all animal groups.
Throughout history, these fish have been of major economic and cultural importance. Today, their ecosystems and habitats make a major contribution to rural employment and leisure tourism. The reasons for their decline are not well understood but pollution, river management and overfishing all play a role.
The EU-funded IMPRESS project is focusing on how better fish-rearing and restocking strategies could help reverse the decline and training the next generation of researchers to oversee new strategies.
“Our main scientific goal is to improve methods for rearing fish intended for restocking into the wild,” says project coordinator Finn-Arne Weltzien of the Norwegian University of Life Sciences. “Most stock fish today are reared for fish farms. This means fish are selected to grow fast and grow big. In the wild, a different set of ‘life skills’ is needed: avoiding predators, finding mates, swimming long distances. With new genetic and fish-rearing techniques, we want to produce fish that can survive better in the wild and reverse population decline.”
Fit-for-purpose fish
Improving wild fish stocks requires a better understanding of complex issues ranging from molecular biology to fisheries management.
“Our young researchers are covering many of these fields,” says Weltzien. “Genetic studies in the Netherlands are giving us a platform to better understand sturgeon life cycles. In France, research is giving insights into how the environment and hormonal changes in young salmon help them move from a freshwater to a marine environment in a river as long as the Loire, on their way to spawning grounds. "
European eels reproduce exclusively in the Sargasso Sea, more than 6 000 km from mainland Europe. Genetic characterisation is providing a resource for better understanding the physiological controls on the eel’s reproductive cycle, a first step towards halting the observed rapid population decline.
The project is also advising hydroelectric dam operators on implementing more fish-friendly dams during migration seasons. Better-adapted fish and improved fisheries management is needed – both of which IMPRESS researchers are promoting.
Social and political aspects
Wider improvements to river and lake ecosystems, and the fish that live in them, requires more than basic science, according to Weltzien. Policymakers need information to act and IMPRESS is contributing to this.
“Our surveys show that the value put on freshwater environments differs from country to country, which is important information for communication campaigns,” says Weltzien.
One outreach initiative is an illustrated children’s book produced by IMPRESS researchers and artists explaining the life cycle of the eel used in promoting science events and as part of activities around fish migration.
“The social dimension is important,” says Weltzien. “For the future, better management of river and lake ecosystems and their fish will need expertise across a range of disciplines.”
Weltzien says IMPRESS introduces young researchers to the range of skills and knowledge that will allow them to be effective and benefit freshwater biodiversity.
Fifteen PhD students based in academic institutions across Europe are part of the IMPRESS training network, which receives funding through the EU’s Marie Skłodowska-Curie actions programme. It involves training-through-research, as well as through secondments and network-wide meetings and events.