Archaeologists in Norway have uncovered evidence that ancient inhabitants of Scandinavia began artificially flooding mountain lakes to create trout reservoirs at least 7,000 years ago. The discovery, detailed in an article published July 20 in the scientific journal Antiquity, stems from research conducted by experts at the University of Oslo and their colleagues.
The team studied five fishing traps found in Lake Tesse, situated at approximately 850 meters above sea level. Radiocarbon dating and dendrochronology analyses revealed that two of the oldest structures were built during the Mesolithic era around 5,000 BC. Two additional finds date to the Neolithic period—3,850 and 2,700 BC.
Scientists propose that Mesolithic hunter-gatherer-fishermen deliberately flooded Lake Tesse by transporting trout from their natural habitats. This practice was necessary because Southern Norway’s interior had been freed of glaciers by 8,000 BC, leaving no fish in newly formed reservoirs and creating landscape barriers that prevented natural colonization. Historically, only trout inhabited Lake Tesse, though the river flowing from it supported over 25 species of fish. Researchers believe ancient people carried trout in specialized water skins to establish these reservoirs.
The study classifies such activities as an early form of productive economy, emphasizing that ancient fishermen exhibited long-term planning—waiting years for trout populations to become suitable for regular fishing. Prior to Lake Tesse being converted into a reservoir in the 1940s, it yielded up to nine tons of trout annually. The first physical evidence of ancient fishing at this site was identified in 2022 by an amateur archaeologist who spotted a trap at low water levels. Subsequent professional excavations in 2023 confirmed that ancient inhabitants used pine, birch, and willow to craft their fishing gear.
