It is not doing well with fish that migrate between rivers and the sea, such as salmon, sturgeon, eel and many others. Since 1970, more than three quarters of these river fish have disappeared worldwide and in Europe even 93 percent. This is evident from a report published Tuesday. One solution: breaking down “one hundred thousand unused dams”.
They are well-known images from nature films: wild salmon that fight against rapids, sometimes hundreds of kilometers upstream from the sea. There are countless other fish species, from the sea trout and the sturgeon to the small stickleback, that have to swim from salt to fresh water to provide posterity. Or sometimes in reverse, like the eel.
“Nowhere are these river fish deteriorating as quickly as in Europe. Besides pollution and climate change, man-made barriers in streams and rivers are the main cause,” Arjan Berkhuysen tells NU.nl.
“Think of dams, ground and weirs: fish simply cannot pass, and lose so much habitat. European rivers have the most barriers. We have recently mapped them all: it turns out to be 1.2 million.”
“We are very proud of our dikes and other waterworks in the Netherlands, but from an ecological perspective they are a catastrophe.”
Klemens Erikksson, waterbioloog
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“River fish served humans for thousands of years”
Berkhuysen is director of the World Fish Migration Foundation, which, together with the World Wildlife Fund, IUCN, the Zoological Society of London and a dozen universities, will Living Planet Index spent on migratory river fish.
“Our conclusion is that it goes extremely bad with itinerant fish species,” says water biologist Klemens Eriksson of the University of Groningen, one of the authors of the report. “We are talking about the near extinction of an entire ecological class that has been abundant in food for thousands of years.”
In order to prevent extinction and to allow fish species to return to their habitats, it is essential, according to Eriksson, to soften the boundary between salt and fresh water.
This can be done by setting up areas with brackish water in coastal zones and by installing fish ladders in sea dikes. “We are very proud of our dikes and other waterworks in the Netherlands, but from an ecological perspective they are a catastrophe.”
“There are dams around the Pyrenees that were built a hundred years ago for hydropower in Spanish villages with a textile industry. When that industry disappeared, the dams simply remained. ”
Arjan Berkhuysen, Director of the World Fish Migration Foundation
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The decline of river fish started in the Netherlands relatively long ago, partly due to the construction of the Afsluitdijk and the Delta Works, but also due to the reclamation of the river land. As a result, river bottoms changed from gravel to mud, which many species cannot deposit eggs on.
Recently, a change in thinking has taken place in the Netherlands, for example by opening the sluices of the Haringvlietdam ajar, allowing the sea lamprey to reach the Maas and Waal again. And in the Afsluitdijk, work is now underway on a ‘fish migration river’, which will allow species to migrate back to the IJssel and Rhine from the Wadden Sea.
Remove old dams for return river fishing
Then there are many other obstacles upstream. Berkhuysen: “For example, there are dams around the Pyrenees that were built a hundred years ago for hydropower in Spanish villages with a textile industry. When that industry broke down and the equipment broke down, the dams simply remained. In total, there are at least one hundred thousand in Europe. . “
In Europe, to restore rivers and streams, a ‘dam removal’-project set up. “Recently, a ninety-year-old, 30-meter-high river dam has been removed in Normandy. Another will disappear in 2021. Then salmon will return. And river fish like trout also benefit, as do sticklebacks, which are food for spoonbills.”
“With nature conservation, we mainly look at land and animals in the air, but we have neglected underwater life for too long. The good news is that the report shows that we can do something about it. Where action has already been taken, it is inspiring to see how quickly nature recovers. “
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