Rhine Tours. Kembs: Repopulating the River with Salmon, the Challenge for Fish Farmers in the Petite Camargue

The operation is nothing exceptional. In fact, Olivier Sommen, director of the Petite Camargue Alsacienne (PCA) fish farm, supported by Kevan Ambiehl, releases salmon fry into the Old Rhine (or the Little Rhine, depending on the flow) at Kembs "three to four times a year" , to repopulate the river first, to combat global warming and also to improve water quality, the presence of salmon in the Rhine serving as an indicator in this area.

This Saturday, June 28th in the morning, as they do once a year, the duo is entitled to an audience for the launching of these 2,500 five-month-old fry, each weighing between 2.5 and 3 grams. The operation takes place in the presence of around thirty people, adults and children. Generous donors since they have all "sponsored" one or more salmon, making a donation of €5 per fish to support the initiative, knowing that it costs double to the PCA for each salmon raised within the Ludovician fish farm . Note that the total is far from the 2,500 sponsored salmon, but local fish farmers take advantage of this to put more fry in the water.

Raised in fish farms since February, these small salmon come from the Loire and Allier rivers, where the eggs were collected from the wild. "When we can, we release Rhine salmon, but we had fewer eggs this year. Rhine salmon had almost completely disappeared a few years ago," explains Olivier Sommen, who is not stingy with explanations to present the salmon's life cycle, its specificities, its acclimatization, and its breeding conditions. "Our salmon have a lot of space in the tanks; we pass a lot of water through them so that they adapt to the current; they are designed for that. And above all, there is no treatment; everything is natural."

Before allowing their godparents to put them in the water in the old Rhine, Kevan Ambiehl, a fish farmer's assistant at the PCA for eighteen months, makes sure that the thermal shock isn't too great. "At the fish farm, they swim in water at 13 degrees; today, the Rhine is at 19 degrees. Transporting them from the fish farm has already raised the temperature a few degrees, but I'm still adding river water little by little so that they get used to this change in temperature. If there's too big a difference, it can shock or kill them."

Ultimately, there are no temperature concerns, but these fry will still have some challenges to overcome, starting with surviving predation from larger fish and fish-eating birds. "With predation, we know we're going to lose about 50% of them," explains Olivier Sommen. "But that's not a bad thing, since it's the liveliest, the best ones that will survive and potentially return to adulthood."

When they reach the beautiful size of 20 centimeters, these salmon will be called smolts and they will leave next spring for a two-month journey towards Greenland. Some will return in three years, bigger, fatter, and taller (nearly a meter), after having gone up the Rhine.

But the return rate is minimal: the director of the Petite Camargue Alsacienne fish farm estimates it at one in 1,000! A drop in the ocean, but a very important drop in the ocean for the PCA fish farmers, who are making progress every year in the major challenge they have set themselves: repopulating the Rhine with salmon.