At a Glance
- Ancient DNA from Lake Redon in the Pyrenees Mountains reveals that humans may have introduced fish as early as the 7th century CE, challenging previous assumptions about the timing of fish stocking.
- The researchers analyzed a 30-centimeter sediment core from the lake, discovering fish parasite DNA from the genus Ichthyobodo. This provides evidence of fish presence as early as the 7th century CE.
- The study found a more consistent signal of fish parasites starting in the 9th century CE, coinciding with nearby archaeological evidence suggesting sheep grazing during the Late-Roman and Visigothic periods.
- The findings indicate that human activities, particularly livestock grazing, may have contributed to introducing fish into the lake, which was likely well-established by the 9th century CE.
- This research highlights the role of ancient DNA in understanding human impacts on ecosystems. It challenges the notion that fish stocking in high-mountain lakes began only in the Middle Ages.
Ancient DNA from a high-altitude lake in the Pyrenees Mountains has revealed that fish may have been introduced to the lake by humans as early as the 7th century CE, much earlier than previously thought. This discovery sheds new light on how human activity has shaped ecosystems, particularly in high-mountain areas like Lake Redon, where fish were once absent due to natural barriers. The findings, published in Nature Communications, suggest that stocking fish in European high-mountain lakes could have started much earlier than the 14th and 15th centuries, which is the period often cited in historical records.
To investigate this hypothesis, Elena Fagin and her team examined a 30-centimeter-long sediment core from Lake Redon, which spans over 3,200 years of history. The core contained DNA from various organisms, but instead of directly finding fish DNA, the researchers discovered DNA from fish parasites, specifically from the genus Ichthyobodo. These parasites are typically found on fish, and their presence provided valuable evidence that fish were present in the lake as early as the 7th century CE. This was long before written records began documenting the introduction of fish into the lake.
The team also found a more consistent signal of fish parasites beginning around the 9th century CE, which coincides with nearby archaeological evidence suggesting the area was used for sheep grazing during the Late Roman and Visigothic periods. This timing suggests that human activity, particularly livestock grazing, may have played a role in introducing fish into the lake. The researchers also noted that fish were likely well-established in the lake by this time, as their presence appeared unaffected by changes in the human population in the surrounding area.
This research demonstrates the potential of ancient DNA to help us better understand the impacts of human activity on ecosystems. It also challenges the common assumption that fish stocking in high-mountain lakes began only in the Middle Ages, providing a much earlier timeline for humans’ influence on these isolated environments. These findings open the door for further exploration of how human settlements may have shaped the natural world in previously unclear ways.
References
- Nature Publishing Group. (2025, April 8). Farmers brought fish up the mountains of Europe as early as the 7th century, ancient DNA reveals. Phys.Org; Nature Publishing Group. https://phys.org/news/2025-04-farmers-brought-fish-mountains-europe.html
- Fagín, E., Felip, M., Brancelj, A., Masqué, P., & Catalan, J. (2025). Parasite sedimentary DNA reveals fish introduction into a European high-mountain lake by the seventh century. Nature Communications, 16(1), 3081. https://doi.org/10.1038/s41467-025-57801-x
