Archaeologists report that hunter-gatherer groups in Norway intentionally introduced fish into mountain lakes about 7,000 years ago, before agriculture spread in the region. According to reports drawing on archaeological evidence, people transported fish into previously fishless mountain lakes to create a reliable food source. After the introduction, they construct wooden traps at the lakes to catch the fish, indicating planned and repeated use rather than a one-time event. One account notes that remnants of these fish traps date back to around 5000 BC, supporting the idea that lake fishing infrastructure was built and maintained over time. The sources also describe the transportation of brown trout, including moving fish past difficult terrain such as waterfalls and rugged landscapes. Overall, the findings point to deliberate ecosystem management by early communities, using both the relocation of live fish and locally built capture technology to sustain access to food.