Archaeologists have uncovered compelling evidence that Mesolithic hunter-gatherers deliberately introduced brown trout into Norway’s mountain lakes around 7,000 years ago, representing one of the earliest known examples of environmental management by prehistoric foraging societies.
The findings, published in the journal Antiquity, are based on the excavation of exceptionally well-preserved wooden fish traps discovered on the exposed lakebed of Lake Tesse in the Jotunheimen mountains of southern Norway. The research suggests that prehistoric communities were actively reshaping ecosystems thousands of years before agriculture became established in Scandinavia.
Lake Tesse is 854 metres above sea level in an area that was completely ice-free around 8400 BC due to the loss of the Fennoscandian Ice Sheet. Although humans quickly settled in the new environment, its steep waterfalls and rugged river systems prevented freshwater fish from naturally reaching the high-altitude lake.
Four stationary fish traps were unearthed from sediments exposed by seasonal changes of water level after the lake was turned into a hydropower reservoir in the 1940s. The best preserved one is a circular trap chamber about 3.5 metres wide, constructed from dozens of tall pine poles linked to a guiding fence that propelled fish into the trap chamber.
Using a combination of radiocarbon dating, dendrochronology and CT imaging, researchers dated the oldest traps to around 5000 BC. Later examples date to approximately 3850 BC and 2700 BC, demonstrating that the fishing technology remained in use and was periodically repaired over a span of more than 2,300 years.
The early dates present a significant archaeological puzzle. Brown trout could not have colonised Lake Tesse naturally, leading the research team to conclude that the fish must have been transported by people.
According to the study, the combination of natural barriers, the absence of alternative fish species and archaeological evidence for intensive fishing strongly indicates that Mesolithic hunter-gatherers intentionally introduced live trout into previously fishless mountain lakes.
The discovery is supported by evidence from numerous other mountain sites across southern Norway, where burnt brown trout bones dating to the fifth millennium BC have been recovered from Stone Age settlements. Together, the evidence points to a widespread tradition of mountain fishing rather than an isolated local practice.
Researchers believe the translocation of fish required sophisticated ecological knowledge. Live trout would have needed to be captured downstream and transported upstream into new lakes, where populations would have taken decades to establish before providing reliable catches. Such long-term planning suggests that Mesolithic communities actively invested in shaping future food resources rather than simply exploiting those already available.
The introduction of trout would have rewritten the economics of mountain hunting. The Jotunheimen region was an important hunting domain for reindeer and elk, but there were substantial dangers. Sustainable fish populations provided a stable source of food to hunt, so hunting groups could stay in the mountains longer and maintain less uncertainty about big game hunting.
The results challenge the long-standing thinking that environmental management came as a result of farming. Instead, the authors state that Mesolithic hunter-gatherers were already capable of complex ecological interventions that permanently altered landscapes.
The introduction of brown trout as a form of early food production, they said, proves that prehistoric foraging societies had the foresight and knowledge to manipulate ecosystems for future generations. Today, there are still descendants of those prehistoric trout populations that support fishing in Norway’s mountain lakes.
Sources : Antiquity – doi:10.15184/aqy.2026.10392
