Watermills spelt the end for Flanders’ salmon, researcher says
Once upon a time, Flanders’ rivers, brooks and creeks were swarming with salmon. But when our ancestors started building mills to harness water power, they unwittingly signed the fish’s death warrant
Driven to extinction
But somewhere around 1300, the salmon stock started to drop, both in Flanders and the Netherlands. How do we know that? By consulting historical documents, like leases, fish permits and reports from fish auctions – in short, every piece of paper that mentioned salmon numbers and prices. And by analysing archaeological remains like old fish bones.
Rob Lenders, an assistant professor in historical ecology at Radboud University Nijmegen, did all that. That’s how he established a clear pattern: from the middle ages, Flanders’ salmon stock suddenly started to drop.
And the decline didn’t stop until the bitter end. By 1900, the salmon population in Flemish and Dutch watercourses was zero.
So what drove salmon to extinction? Overfishing and water pollution are both obvious reasons, but on closer inspection, they don’t satisfy. “The Scots fished as much as the Flemish for salmon,” says Lenders. “And serious water pollution only started much later, during the industrial revolution.”
According to his research, a totally unexpected factor finished the salmon off: watermills. “From the year 1000, we see watermills arise at every possible location in Flanders,” he explains. “At one point the total number of mills must have exceeded 10,000.”
Flemish-designed watermills were particularly problematic for salmon, as they were generally accompanied by a little dam, to increase the water fall. “Obviously those dams formed a barrier for salmon needing to swim upstream,” says Lenders.
But aren’t salmon known for their ability to go against the flow and jump over obstacles? “They are,” Lenders admits, “and the stronger ones will indeed have succeeded in travelling all the way to their spawning grounds. But the dams didn’t only stop the weaker specimens, they also took the current out of the water. As a consequence, the beds of ballast in the upstream parts of the rivers and creeks were covered with a thick layer of sand and silt, which made them unsuitable for spawning.”
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