Why isn't the salmon making a comeback in Switzerland?

The return of salmon in Switzerland has so far been a flop. Experts are dismayed and are looking for answers. First the good news: young salmon, thousands of which are released in Switzerland every year, manage to swim towards the sea. This is not something to take for granted, as they swim in the middle of the river and must deal with turbines at power stations on the river. They run the danger of being chopped up or crushed. Take the small river Bünz in canton Aargau, for example. The fish have to pass through three turbines on the way to the Rhine. "Around 81% made it, which was a positive surprise for us," says fish ecologist Armin Peter. He tagged the fish for a study. There are a further 14 turbines to the lowest power station in the Rhine. "There are actually young salmon that survive this journey," says Peter, who is investigating this in another ongoing study. Number of returnees decreases drastically There has also been good news for a long time about the return...