Hunter-gatherers introduced fish to a mountain lake 7000 years ago
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- Axel Mjærum at the University of Oslo says hunter-gatherers moved brown trout into the Norwegian highlands at least 7,000 years ago — the oldest documented example of human-mediated fish translocation in the world.
- Lake Tesse, at 850 metres elevation, sat under the Fennoscandian ice sheet until roughly 8,400 years ago; before its 1940s conversion for hydropower, it produced 9 tonnes of brown trout a year, with waterfalls ruling out natural fish dispersal.
- Wooden fish traps uncovered in 2022 when the lake was partially drained were radiocarbon-dated to about 4950 BC, and tree-ring analysis of two younger posts pinned them to spring 2669 BC and winter 2657-2656 BC, showing the structures were maintained over generations.
- The fish stocking predates farming in Scandinavia by centuries, though Mjærum notes that eel traps and channels in Australia date to 8,600 years ago as an even earlier example of managed fish harvesting.
- Mjærum says the fish were likely carried in waterskins, and a predictable food supply let whole family groups — not just big-game hunters — extend their stays in the mountains during summer.
Why it matters: This finding pushes human environmental management back centuries before Scandinavian agriculture, recasting hunter-gatherers as active ecosystem engineers rather than passive foragers. With Lake Tesse's 9-tonne annual trout yield now traced to a 7,000-year-old stocking event, archaeologists have a new benchmark for when and how humans began reshaping animal populations worldwide.
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