Ancient fish traps found in Norway’s mountains show that Stone Age hunter-gatherers reshaped remote landscapes thousands of years before farming reached the region. Researchers say the communities introduced brown trout into lakes that had no natural fish populations. They then built permanent wooden structures to harvest the new food source.
The traps were discovered at Lake Tesse in the Jotunheimen mountains of southern Norway. The lake sits about 854 meters, or 2,802 feet, above sea level.
Axel Mjærum led the study, which examined four stationary fish traps preserved beneath the lakebed. Dating showed that the earliest structures were built around 5000 BC. Later traps date to about 3850 BC and 2700 BC.
The findings suggest fishing continued at the lake for at least 2,300 years. They also challenge the traditional belief that people began managing natural resources only after the rise of agriculture.
Wooden traps reveal complex engineering
The traps came to light after water levels at Lake Tesse were lowered. The lake became a hydropower reservoir in the 1940s. Its water level now falls each spring, exposing parts of the former lakebed. Researchers excavated four traps after the first structures were identified in 2022.
The best-preserved example contained 46 wooden poles. About 40 of them formed a chamber measuring roughly 3.5 meters, or 11.5 feet, across. Six other poles appear to have formed a guiding fence that directed fish into the chamber.
Some poles carried cut marks, splits, and possible signs of binding. Most stood vertically and may have supported a woven wall. Angled poles reinforced the structure.
The builders mainly used young Scots pine. They also used birch and willow. Evidence from the wood suggests people cut many of the trees during spring or early summer, when the traps were probably built and used.
People carried trout into fishless lakes
Researchers say brown trout could not have reached Lake Tesse naturally. Glaciers once covered much of inland Norway, leaving its lakes without freshwater fish. After the ice melted, steep rivers and waterfalls prevented fish from swimming into many high mountain waters.
Only brown trout appeared in several ancient mountain fishing sites. Researchers say that pattern is difficult to explain through accidental transport by birds or other natural forces.
The evidence instead points to deliberate human action. Stone Age communities likely caught live trout in lower waterways and carried them uphill in containers, possibly made from animal skins.
The fish would have needed years to reproduce in sufficient numbers. This required patience and detailed knowledge of fish biology. It also meant that the people who introduced them may not have received the main benefits themselves.
Fishing made mountain life safer
The new trout populations provided a reliable food supply for groups visiting the mountains to hunt elk and reindeer. Big-game hunting could be dangerous and unpredictable. Fish gave communities a dependable source of fresh food. This may have allowed larger groups to remain in the mountains for longer periods.
The Lake Tesse traps show that hunter-gatherers did not simply search for available resources. They transformed an ecosystem to create a lasting food source. Brown trout still live in many Norwegian mountain lakes today. Their presence may be part of an environmental legacy that began with Stone Age communities about 7,000 years ago.
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