Barely a century ago, the river Eira was known for its population of large-grown salmon. An average salmon caught in Eira was then 12 kilos and among the largest in the world, but today the average weight is four kilos. The size has been reduced to a third over the course of several decades. Ingerid Julie Hagen is one of those at NINA who has researched why it has happened, and now the new report is out. It shows that reduced flow in the river is the cause. Within a few generations, the salmon have adapted to the low water flow and shrunk. Wanda Thoresen with large salmon from Eira before the regulation of the watercourse. Photo: Engelskhuset Ellen K. Fagerslett with Eira salmon after the regulation of the watercourse, in 2009. Her salmon weighs 7.5 kilos, which is well above today’s average. Photo: Dag Ringstad Kenneth B. Eilertsen and Torgeir Fagerslett with Eiralaks in 2020. Photo: Dag Ringstad – Man-made changes The flow of water in the Romsdal River has been gradually reduced by three different power developments. In the report, they have compared river flow and salmon size in the same period. It clearly shows that the size of the salmon has decreased in line with the amount of water. The research report from NINA Photo: NINA Changes in flow and body mass of Atlantic salmon in the river Eira: The red line shows a ten-year rolling average of annual flow in the river Eira from 1940 to 2016. The blue line shows the average body mass in kilograms of individual salmon from 1925 to 2016. The dashed vertical lines show when the three different power developments took place. The graph shows that the salmon have become smaller, at the same time as the amount of water has decreased. – This is an example of rapid evolution in a natural population, where changes are driven by man-made changes. Researcher Ingerid Julie Hagen at NINA. Photo: Arnstein Staverlokk This is what researcher Ingerid Julie Hagen says, and adds: – And man-made changes are now taking place over almost every ecosystem in the entire world, but it is still difficult to observe. In this publication, we have documented it very clearly. According to the researcher, the genetic material for becoming small salmon could be found in the Eira population even before the power developments, but at a lower frequency. What has now happened is that the gene for becoming small salmon has increased. In this way, a larger part of the stock becomes small salmon, explains Hagen. I don’t think they will get back the world’s largest salmon Kirsti Fagerslett is the leader of the Eira river owners association. She says it is good to substantiate the connection that it is a lack of water that causes the genes of the salmon to change. She does not think they will get the large salmon back again, unless there is more water. – With a little more water, we can increase the population through larger spawning and rearing areas, says Kirsti Fagerslett, leader of the Eira river owners association. Photo: Øyvind Sandnes / news – The amount of water that was there in the past needs to be restored, but we can at least raise it a little. And the researchers believe that the genes are still there, so greatness can return. But the biggest salmon in the world, I’m afraid we won’t be able to brag about ourselves again. Fagerslett believes it is important to keep a cool head, and not just think about the climate and global warming of the globe. – We have to think about the whole natural diversity. We will manage the salmon and several red-listed species. Then we must be able to think about both the climate and the environment. Elva Eira last week. Photo: Dag Ringstad / news – The authorities decide Statkraft is behind the power developments in Eira. Senior specialist in the environment at Statkraft, Eirik Bjørkhaug, says they are aware that regulation of waterways affects the environment, and that the relationship with salmon has become worse. – We work a lot to reduce negative environmental impacts in waterways where we are regulators, says Eirik Bjørkhaug, senior environmental specialist at Statkraft. Photo: Private – We take care of authority processes. The license has now been revised, so it will be around 30 years until the next time this question is raised. It is the authorities who decide whether we will release minimum drainage in Aura, says Bjørkhaug. Statkraft follows the concession they have received. They do not let in more water than they should, and they also do not increase the flow of water, explains Bjørkhaug. Now they are working on a plan for salmon in the entire Aura watercourse. – Then we will see if there are other measures we can take other than increased water discharge. For example, if you change the course of the river or work on reopening some side courses. Perhaps the conditions for fish can be made better like this, instead of the minimum water flow. The picture of salmon fishing in Eira was taken in August 2017. Photo: Kirsti Fagerslett
ttn-69
New research from NINA shows that the salmon in the river Eira have shrunk due to water power – news Møre og Romsdal – Local news, TV and radio
