Archaeologists have uncovered the remains of 7000-year-old fish traps in the mountains of southern Norway, indicating fish were intentionally introduced to upland lakes by Mesolithic hunter-fisher-gatherers and showing how human management of nature was not limited to agricultural societies.
Following glacial retreat c. 8000 BC, humans first began migrating into the mountains of inland southern Norway, but natural barriers such as waterfalls prevented fish from swimming into the region on their own.
Instead, freshwater fish were introduced to upstream lakes and rivers by humans, who moved them from their natural habitats in order to harvest them. It was unknown, however, when this took place.
“For more than 100 years, it has been known that the fish inhabiting watercourses in the Norwegian mountains are descended from specimens translocated by humans”, says lead author of the research, Axel Mjærum from the University of Oslo. “However, until now it has remained unclear when people first began transporting fish upstream into lakes and rivers that originally lacked natural fish.”
Therefore, the discovery of several preserved wooden fish traps at Lake Tesse, in the southern Norwegian mountains, provided an opportunity to tackle this problem.
The research team radiocarbon dated the traps, finding that they were in use from 5000 BC onwards. “This implies that fish—and more specifically brown trout (Salmo trutta)—were translocated by hunter-fisher-gatherers during the Scandinavian Mesolithic”, Mjærum explains.
Brown trout can achieve a considerable size, are calorie rich and are relatively easy to catch; making them the perfect choice to introduce into new waters for fishing.
Importantly, the Scandinavian Mesolithic refers to a period prior to the adoption of farming, meaning that the people who made the traps, and therefore translocated the fish, were hunter-fisher-gatherers.
These findings indicate hunter-fisher-gatherers in Scandinavia were actively managing their environment to control their food supply. It could even be seen as a form of early food production, illustrating the capacity of pre-farming societies to deliberately interact with and transform ecosystems.
The impact of this introduction persisted into the Neolithic and can still be felt to this day, with modern fishers continuing to harvest the brown trout descended from those first introduced to Lake Tesse thousands of years ago.
“Hunter-fisher-gatherers’ release of brown trout into previously fishless lakes in the Norwegian mountains around 5000 BC is a very clear example of humans’ general capacity to reshape entire ecosystems, even before the introduction of farming”, Mjærum concludes.