Introduction
Human management of natural resources has traditionally been viewed as coeval with the development of farming practices and is considered one of the most important turning points in prehistory, fundamental for the development of more complex societies. Yet, this perspective creates a binary distinction between hunter-fisher-gatherer and agrarian societies that can restrict interpretation of the archaeological record. Since the 1970s, a theoretical shift, accompanied by methodological advances in archaeology, has led to a more nuanced view of hunter-fisher-gatherer societies and their diverse subsistence strategies (e.g. Woodburn Reference Woodburn1982; Kelly Reference Kelly2013: 248–52). There has also been an increased focus on the dynamic relationships between humans and nature, and on traditional ecological knowledge (e.g. Berkes Reference Berkes2012).
These approaches acknowledge that many hunter-fisher-gatherers were low-level food producers who employed techniques such as tilling, harvesting, burning and weeding. They also engaged in the transportation and seeding of plants, predator control and the management of large game populations (e.g. Berkes et al. Reference Berkes2000; Grøn & Turov Reference Grøn, Turov and Hårdh2007: 71). However, examples of such complex resource management among prehistoric hunter-fisher-gatherers are still relatively scarce. In this context, the new discovery of Mesolithic stationary fish traps in Lake Tesse, located in the mountains of southern Norway, helps increase our understanding of such complexity.
The context of research
For most of the last glacial period (c. 115 000–9700 BC), much of inland Norway lay beneath the Fennoscandian Ice Sheet (Stroeven et al. Reference Stroeven2016). During the Pre-Boreal (9700–8200 BC), the ice sheet gradually receded and large parts of central southern Norway were deglaciated by 8000 BC (Romundset et al. Reference Romundset2023). The ice coverage during the last glacial period rendered inland habitats inhospitable to freshwater fish; thus, all freshwater species currently occupying inland Scandinavia must have arrived after the ice retreated.
In parts of the lowlands, fish were able to naturally colonise waterways, migrating from coastal zones and from the former freshwater and brackish water stages of the Baltic Sea in the Early Holocene (Hesthagen & Sandlund Reference Hesthagen and Sandlund2004). During these migrations, regionally high but gradually receding relative sea levels were an important factor, allowing multiple fish species to reach extensive inland areas. However, certain regions above the maximum sea level—the marine limit—remained devoid of natural fish populations; steep gradients and waterfalls served as topographical barriers, preventing the natural migration of fish up some watercourses.
The Early Holocene deglaciation also opened the landscape of central and northern Scandinavia for human habitation (Manninen et al. Reference Manninen2021). From around 8300 BC onwards, more complex and semi-sedentary hunter-fisher-gatherer societies began to develop in this region, relying heavily on biodiverse and thriving marine environments, with a strong emphasis on fishing (Mansrud & Persson Reference Mansrud, Persson and Persson2018; Bergsvik & Ritchie Reference Bergsvik, Ritchie and Schülke2020). During the Mesolithic (until 3900 BC) and Neolithic (3900–1700 BC) periods, communities ventured inland in search of resources, including large game such as elk (Alces alces) and reindeer (Rangifer tarandus), with some groups possibly staying in inland areas year-round (Bjerck Reference Bjerck, Bailey and Spikins2008: 104–105; Damlien & Solheim Reference Damlien, Solheim and Blankholm2018). Rivers and lakes in most high inland areas were devoid of fish, so fishing based on naturally spread fish populations was not possible.
The case of Lake Tesse
Lake Tesse, originally spanning 12km2, is situated 854m above present sea level (apsl). This low alpine lake lies within the central Norwegian mountain region of Jotunheimen, an area that underwent deglaciation around 8400 BC (Romundset et al. Reference Romundset2023). The lake is drained by the steep Tessa River, culminating in Lake Vågåvatnet (362m apsl), which ultimately drains into the Oslofjord (Figures 1 & 2). Historically, the lower part of this watercourse supported around 25 different fish species, while only brown trout (Salmo trutta L.) were known in the upper part (Huitfeldt-Kaas Reference Huitfeldt-Kaas1906: 24, Reference Huitfeldt-Kaas1918: 21–24).
Location of Lake Tesse, the fish traps in Dågåtjønnvikje and the Stone Age sites surrounding the bay (figure by authors).
The large watercourses in the Jotunheimen mountain area linking sites with early dates of fish bones and fishing gear. The red arrows mark a likely pathway for the transport of living fish to Lake Tesse (apsl: above present sea level) (figure by authors).
Before Lake Tesse was transformed into a hydropower reservoir in the 1940s, it was renowned as one of the most productive brown trout lakes in Norway, yielding up to 9000kg annually, equivalent to 7.4kg/ha (Hesthagen & Gunnerød Reference Hesthagen and Gunnerød1980: 108). Annual lowering of the water level each spring exposes extensive areas of the former lakebed, which creates opportunities for archaeological discoveries. Finds from drained parts of the lake underscore the enduring importance of fishing in Lake Tesse, with evidence of fishing in the Viking Age and the medieval period (from c. AD 800), particularly in the south-western part of the lake. Fishnet sinkers resembling those typically linked to contexts from the third millennium BC have also been discovered (Indreko Reference Indreko1956: type A, cf. Mjærum Reference Mjærum, Mjærum and Wammer2016: 72).
Multiple Mesolithic and Neolithic sites have been identified along the lake shore, and small parts of these have been excavated. Charred elk bones discovered at one site provide some of the earliest evidence for human activity; two of these bones have been radiocarbon dated to approximately 7000 BC. Other radiocarbon dates and artefacts indicate activity around Lake Tesse throughout Mesolithic and Neolithic (see online supplementary material (OSM) for details). In 2022, an area containing fish traps was uncovered on the dredged lakebed in the south-western part of Lake Tesse, prompting a more extensive excavation project.
Methods
Four fish traps (traps 1, 2, 3 & 5) were manually excavated from the dredged lakebed (Figure 3). Trap 5 was fully excavated, while approximately 50mm of topsoil was removed from around traps 1, 2 and 3, suggesting that only portions of the poles associated with these three structures were identified. All visible poles and the surrounding lakebed were documented (see Friis Reference Friis2025 for details). As part of this investigation, 113 larger wooden samples were collected for dendrochronological analysis, of which 73 are interpreted as components of separate poles used in the construction of the four traps.
The fish traps at Lake Tesse, with sections of the Stone Age settlement area visible in the background (figure by authors).
Specimens were identified to species or genus by microscopic analysis (Mork Reference Mork1966). Tree rings were initially studied on frozen surfaces prepared with a blade and chalk. Poor preservation meant that the remaining specimens needed to be air-dried, stabilised with a resin (G-Stab 5050, main components: polyglycol dimethacrylate and lauryl methacrylate) and subsampled with a sliding microtome. Tree-ring widths were measured to the nearest micron using a Velmex TA measuring system. On five poles, ring widths were determined digitally from computed tomography (CT) images at a resolution of 14–25μm. In cases of compressed wood, measurements were taken along the radial cell walls, rather than along the shortest distance across a ring.
Implemented dendrochronological dating methods included tBP statistics (Baillie & Pilcher Reference Baillie and Pilcher1973) and the sign test (Gleichläufigkeit) (Hollstein Reference Hollstein1980), as well as the use of the crossdating and measurement quality-control programme Cofecha (Holmes Reference Holmes1983; Speer Reference Speer2010). Due to the brevity of the sampled tree-ring series, it was essential to perform visual assessments of growth patterns. Identification of fragments of the same poles was possible in some cases based on stem diameter/number of tree rings and even patterns of compressed wood and discolouration. On seven poles, the outermost tree ring was radiocarbon dated. Six other poles were dated by radiocarbon wiggle matching. Altogether, these radiocarbon dates represent all the four excavated traps, while trap 1 has also been absolutely dated by dendrochronology.
Results
The fish traps
Trap 5 comprises 46 preserved poles: a concentration of 40 standing poles delineates a chamber approximately 3.5m in diameter (Figures 4 & 5), while six additional poles are interpreted as part of a guiding fence leading to this chamber. Despite notable erosion in certain areas of the fish trap (see OSM), several of the best-preserved poles show evidence of having been crafted, including numerous cut marks, splits and potential traces of lashing. Most of the poles were positioned vertically in the lakebed and likely supported some form of lattice wall. This type of construction is known from previous finds in the north-western European lowlands, with records dating its use back to approximately 4000 BC (Bērziņš Reference Bērziņš2008; Koivisto Reference Koivisto, Groß and Rothstein2023), while enduring utility is corroborated by more recent archaeological and ethnological records (Sirelius Reference Sirelius1906; Claesson Reference Claesson1937; Valonen Reference Valonen1953; Mjærum et al. Reference Mjærum2024). Additionally, 11 of the poles were set at a 30–45° angle and likely functioned to support the vertical poles, thus reinforcing the overall structure.
Left) plan and photograph of trap 5; right) 3D rendering and in situ photograph of one of the best-preserved poles in the trap (A518) (figure by authors).
Figure 4 Long description
The image consists of three elements: one diagram, one photo, and one illustration. The diagram and photo on the left show a plan and photograph of a fish trap. The diagram includes a scale in meters and labels for the fish trap and poles. The photo shows the actual fish trap in situ with yellow and blue dashed lines indicating the structure. The illustration and photo on the right show a 3D rendering and in situ photograph of a well-preserved pole (A518) within the trap. The 3D rendering highlights cut marks, breaks, and taphonomic deformation along a 500 millimeter scale. The in situ photo provides a real-world view of the pole in the ground.
Examples of poles from the Lake Tesse fishing traps (figure by authors).
Detailed dendrological analysis of 73 poles reveals similarities in the wood used in the four traps. In constructing the fish traps, stems of small trees were employed, predominantly Scots pine (Pinus sylvestris), supplemented with a few birches (Betula sp.) and willows (Salix sp.). The average stem diameter is 37mm (ranging from 15–95mm). While most samples preserve both the inner pith and the outer waney edge, the average number of tree rings is just 32, spanning from five to 110 rings. Consequently, a considerable proportion of the ring widths reflects juvenile growth, which typically deviates from the expected regional growth pattern essential for tree-ring dating.
Among the poles with preserved waney edges, growth ended with earlywood (n = 19) and latewood (n = 18) in almost equal proportions. Earlywood at the waney edge indicates trees felled early in the growing season, while those concluding growth with latewood were cut during the cambium’s dormant period, lasting until late May or early June (Karlsen et al. Reference Karlsen2020: 18). This suggests that the traps were predominantly constructed using trees felled during spring and early summer. This is consistent with the use of similar traps in more recent times in the Nordic countries: traps were constructed in the spring and caught fish throughout the summer (Sirelius Reference Sirelius1908: 302; Valonen Reference Valonen1953; Mjærum et al. Reference Mjærum2024: 39).
Radiocarbon analysis of seven poles, using calculated logging years, univocally dates the excavated trap 5 to the Late Mesolithic, around 4950 BC (Figure 6). Despite severe erosion, which limited detailed interpretations of the construction of the fish trap, we observe clear parallels between trap 5 and the remaining traps in Lake Tesse. Trap 2 is also radiocarbon dated to approximately 5000 BC, while trap 1 is dated to 3850 BC and trap 3 to 2700 BC (Figure 6 and OSM). More specific dating was attempted by correlating the dendrochronological findings with the most comprehensive pine tree-ring chronology available for the central Scandinavian mountains. This chronology is based on records from Jämtland, Sweden, covering a period from 4868 BC to AD 2006 (Gunnarson Reference Gunnarson2008). Consequently, two posts from trap 1 are regarded as having an absolute date. One was felled between spring 2669 BC and winter 2669/2668 BC, while the other dates to winter 2657/2656 BC or shortly thereafter, indicating that the poles were erected approximately 12 years apart. This dating interval suggests that the traps were periodically maintained, a practice previously documented in a medieval lattice-wall fishing trap from Nord-Mesna, south-east Norway (Mjærum et al. Reference Mjærum2024). These analyses date the construction and use of the traps in Lake Tesse to 5000 BC onwards.
Radiocarbon dates from the fish traps at Lake Tesse. The plot is based on all 25 radiocarbon dates, of which 18 are included in the six wiggle-matched dates. Additionally, a sum diagram of dates (n = 13) from settlements around the lake is presented at the bottom (figure by authors).
Figure 6 Long description
Panel A: Trap 1. A timeline showing felling dates for poles A104 and A112, both wiggle matched, spanning from around 6000 BC to 4000 BC. Panel B: Trap 2. A timeline showing the outer year-ring date for pole A215, around 5000 BC. Panel C: Trap 3. A timeline showing felling date for pole A306, wiggle matched, and outer year-ring dates for poles A405 and A306, spanning from around 5000 BC to 3000 BC. Panel D: Trap 5. A timeline showing felling dates for poles A563, A515, A541, and 503, all wiggle matched, and outer year-ring dates for poles A532/A566, A505, and A518, spanning from around 5000 BC to 2000 BC. Panel E: Settlements. A sum diagram of dates from 13 settlements around Lake Tesse, spanning from around 8000 BC to 2000 BC.
Discussion
Early fish in mountain areas
The early dates of the fish traps at Lake Tesse are, so far, unique within the mountainous regions of southern Norway but there is evidence that fishing in Lake Tesse was part of a broader tradition. Extensive archaeological surveys have documented hundreds of Mesolithic and Neolithic settlements positioned in proximity to contemporary prime fishing areas in the southern Norwegian mountains, implying that fishing was a crucial factor influencing the selection of settlement locations (e.g. Indrelid Reference Indrelid1977: 132–33). With its settlements, the area around Lake Tesse was interpreted as a Stone Age fishing ground long before the traps were discovered in 2022 (Hagen Reference Hagen1959).
Further, despite substantial taphonomic losses, partially due to the region’s acidic soils, contexts with burned fish bones have been identified and radiocarbon dated at nine sites in the Jotunheimen and Hardangervidda mountains. All these contexts pre-date 1700 BC, with five dating to the fifth millennium BC, making them approximately contemporaneous with the earliest dates for the fish traps from Lake Tesse (Figure 7) (for details, see Mjærum Reference Mjærum, Mjærum and Wammer2016: 240–49; Mjærum & Mansrud Reference Mjærum, Mansrud and Schülke2020: 272). All of these sites are situated beside lakes connected to extensive watercourses. At seven sites, detailed taxonomic study of fish bones has been conducted and only the remains of brown trout are identified. This finding is consistent with the fact that brown trout was the sole species present in these high-altitude lakes until recently. Moreover, the absence of other fish species makes it unlikely that fish were caught in coastal or lowland regions and then transported to mountainous areas as preserved food; lowland fishing regions, and the aquatic assemblages reflecting their exploitation, are typically more biodiverse (e.g. Mansrud & Persson Reference Mansrud, Persson and Persson2018).
The dated fish traps at Lake Tesse: compiled calibrated probability distribution of Stone Age contexts associated with fishing in the mountains of southern Norway. Brown trout is the only identified species at eight sites, while the fish bones at Lake Røyrtjønna remain undetermined. In addition, a context with two net sinkers and a bone fishhook at Lake Olstappen has been dated to around 2800 BC. Areas correspond to those identified in Figure 2 (figure by authors).
Human introduction of fish into mountain areas
Arguments have been made for the natural dispersal of fish and fish eggs across dry land, especially through transport by birds, but it is difficult to find examples verifying the avian spread of fish to fishless lakes (Hirsch et al. Reference Hirsch2018). In the context of the Norwegian mountains, there are also more specific arguments against this hypothesis. Firstly, brown trout were the only fish species present in most mountain lakes (Huitfeldt-Kaas Reference Huitfeldt-Kaas1918), such species-specific consistency is challenging to explain through bird-mediated dispersal. Avian transport also fails to account for what appears to be the relatively synchronic emergence of mountain fishing from approximately 5000 BC onwards.
Given the lack of natural fish populations after deglaciation, the barriers formed by waterfalls, the absence of natural vectors capable of transporting fish and fish eggs past these obstacles and historic distribution patterns of fish species in the Norwegian mountains, it can instead be concluded that fish in the mountain lakes must have been introduced by human activity (cf. Huitfeldt-Kaas Reference Huitfeldt-Kaas1918). Brown trout can achieve a considerable size, are calorie rich and are relatively easy to catch; these traits likely made them the preferred choice for introduction into new waters.
Humans have introduced brown trout and various other fish species into lakes around the world, with a significant increase in these introductions following the establishment of the first fish hatcheries in the mid-nineteenth century (Pister Reference Pister2001). The fishing rights for mountain lakes are mentioned in several European texts from the fourteenth century onwards (Ugulen Reference Ugulen, Mjærum and Wammer2016; Ventura et al. Reference Ventura and Catalan2017: 182–3), implying that fish had already been introduced to these lakes. The practice of carrying fish to a new lake is also explicitly referenced on a Norwegian runic stone from the twelfth century (Eknæs Reference Eknæs1979: 9–10). In the Spanish Pyrenees, analysis of sedimentary ancient DNA indicates the presence of fish introduced by humans during the fifth century AD (Fagín et al. Reference Fagín2025). The brown trout from the Norwegian mountain lakes now substantially extend this timeline for human introduction of fish.
The practice of introducing fish into Norwegian mountain lakes
The genetic diversity among trout in Norwegian mountain watercourses indicates that these ancient translocations were conducted upstream within river systems, on multiple occasions and as stepwise processes (Sønstebø et al. Reference Sønstebø2007; Heggenes Reference Heggenes, Mjærum and Wammer2016). Such a practice of transporting fish upstream and into new lakes is well documented in Norway over the past few centuries (e.g. Huitfeldt-Kaas Reference Huitfeldt-Kaas1918: 66; Severinsen Reference Severinsen, Mjærum and Wammer2016: 174–76). Whether conducted in recent times or in the distant past, translocation requires entanglement (cf. Hodder Reference Hodder2012: 138–39) with the process encapsulating not only the fish but also various other things, including fishing equipment, containers for transporting fish and pathways connecting lowland and mountainous areas. Limited information is available regarding how this was practically organised during the Mesolithic. Trap fishing, such as that practiced at Lake Tesse, was likely one of several methods available for catching live fish. Waterskins may then have been used to carry the fish, as evidence for the processing of hides and skins features prominently in the archaeological record of Mesolithic Norway (cf. Skandfer Reference Skandfer2022).
Regardless of the specific methods used for these translocations, it would have taken several decades for the fish population to reproduce to levels sufficient for substantial catches in Lake Tesse and other similar lakes (cf. Huitfeldt-Kaas Reference Huitfeldt-Kaas1927: 108–18). To successfully transport fish and anticipate this delayed return (cf. Woodburn Reference Woodburn1982), knowledge of fish biology and ecology was also essential. It is recognised that foragers often possess a deep understanding of their environments, commonly referred to as traditional ecological knowledge (e.g. Barkes Reference Berkes2012). Such insights result from long-lasting and profound entanglements between these societies and their surroundings, and they are used to interact with, adapt to and manage these environments, including both animals and plants (e.g. Viveiros de Castro Reference Viveiros de Castro1998; Berkes et al. Reference Berkes2000; Grøn & Turov Reference Grøn, Turov and Hårdh2007). Norwegian Mesolithic societies were heavily dependent on aquatic resources, which provided a strong foundation for their knowledge of fish ecology (cf. Mansrud & Persson Reference Mansrud, Persson and Persson2018; Bergsvik & Ritchie Reference Bergsvik, Ritchie and Schülke2020).
Motivations for introducing fish
Big game hunting traditionally held significant value within foraging societies, not only for its tangible returns but also for the prestige it conferred (e.g. Grimstead Reference Grimstead2010; Kelly Reference Kelly2013: 221–2, and references therein). This also seems to have been the case in the Norwegian Mesolithic, even though these populations based much of their lives on aquatic resources. The archaeological record of the region—featuring rock art panels and zooarchaeological assemblages dominated by ungulates (e.g. Fuglestvedt Reference Fuglestvedt2018), sites located along elk and reindeer migration routes and hunting equipment in the form of projectile points—underscores the cultural importance of big game during the later part of the Mesolithic (e.g. Glørstad Reference Glørstad2010).
Most of the best hunting grounds for elk and reindeer were located inland (Mjærum Reference Mjærum and Persson2018), which may have necessitated mountain visits to access these animals. A traditional migration route for reindeer passes near Lake Tesse, and elk inhabit the surrounding forests, making the area a prominent destination for hunting. The Langfonne ice patch in the high mountains, just 11km west of Lake Tesse, has served as a reindeer hunting ground since at least the fifth millennium BC (Pilø et al. Reference Pilø2018). Nevertheless, venturing into the mountains carried inherent risks that exacerbated the unpredictable nature and relatively low success rates of big-game hunting.
The introduction of fish to these mountain hunting grounds would have been transformative, expanding the resource base to include a secure, fresh and nutritious staple food. In this way, the mountain environments became more like lowland areas, to which these populations were already well adapted. Fish would have drastically mitigated the risks associated with extended stays in the mountains, making it feasible for more people to remain in the area for longer. Furthermore, it facilitated the harvesting of other coveted mountain resources, such as fur and lithic raw materials.
Resource management among hunter-fisher-gatherers
The early introduction of fish to the Norwegian mountains serves as a clear illustration of resource management among prehistoric hunter-fisher-gatherers, but it is by no means a unique instance of such a practice. Recent decades have revealed numerous resource-management strategies rooted in human-environment entanglements and a profound understanding of accumulated environmental knowledge.
A notable early example is the domestic dog, which has accompanied humans in vast translocations for over 15 000 years (Bergström et al. Reference Bergström2026; Marsh et al. Reference Marsh2026). Other examples include the introduction of the mountain hare (Lepus timidus) to the island of Gotland in the Baltic Sea around 7000 BC, as well as its reintroduction around 2800 BC, likely undertaken by humans to enhance hunting opportunities (Ahlgren et al. Reference Ahlgren2016). Similar introductions aimed at improving hunting occurred at later stages in other parts of Europe, such as the translocation of red deer (Cervus elaphus) during the Early Neolithic in Ireland (Montgomery et al. Reference Montgomery2014: 157).
Another instance of early human environmental influence is the deliberate or accidental role humans played in facilitating the rapid spread of the hazel tree (Corylus avellana) in Europe following the last Ice Age (Tallantire Reference Tallantire2002: 85). As the tree spread, their nuts became a vital component of the Mesolithic human diet, while stems could be used for wickerwork such as fish weirs and traps. Charcoal found in Mesolithic pollen records indicates that hunter-gatherer communities also used fire to improve the conditions for hunting ungulates (Selsing Reference Selsing2016: 72; Nikulina et al. Reference Nikulina2025).
Based on the dates from the fish traps at Lake Tesse, the translocation of brown trout in the Norwegian mountains likely began no later than 5000 BC. In southern Scandinavia, indications of contact with continental European farmers emerge from around 5500 BC, while the earliest evidence of husbandry and cereal farming dates to around 4200 BC (Sjögren Reference Sjögren and Hofmann2025). In the central region of Scandinavia, which is the primary focus of this article, the period 6300–4500 BC is associated with increased societal complexity in hunter-fisher-gatherer populations (cf. Bjerck Reference Bjerck, Bailey and Spikins2008: 104–105; Glørstad Reference Glørstad2010), but clear evidence of interaction with farming groups during the Mesolithic (prior to 3900 BC) is absent (Bergsvik et al. Reference Bergsvik and Gron2020; Solheim Reference Solheim and Schülke2020). Indications of farming are known from approximately 3900 BC, but hunting, gathering and fishing remained the primary subsistence strategies until around 2200 BC (Solheim Reference Solheim2024). The first translocations of fish in the Norwegian mountains were thus clearly conducted by hunter-fisher-gatherers.
In a dichotomous narrative, the transition to the Neolithic signifies a pivotal moment when humanity transformed from passive participants in nature into environmental managers capable of developing complex tools, societies and civilisations. Yet, the translocation of fish by Mesolithic groups should also be recognised as an example of environmental management, both of fish populations and of the mountain environment. In fact, it can be considered a form of food production among hunter-fisher-gatherer communities and provides just one of an increasing number of case studies that illustrate the capacity of pre-Neolithic human societies to interact with and impact entire ecosystems and the organisms that inhabit them (cf. Berkes Reference Berkes2012; Spengler Reference Spengler2021: 935–36). These findings contribute to ongoing discussions about societies traditionally considered non-complex, challenging previous notions of a qualitative distinction between pre-agrarian and agrarian societies (cf. Woodburn Reference Woodburn1982; Lightfoot et al. Reference Lightfoot2013: 287–90) and the simplified idea that hunter-fisher-gatherer societies are searchers for resources, while agricultural societies are food producers (cf. Hayden Reference Hayden1990).
By introducing brown trout, a strong and lasting entanglement was established between people and aquatic resources in the mountains (cf. Hodder Reference Hodder2012: 195–200). These ties continued to shape activities in the region during the Neolithic, as evidenced by the construction of new fish traps in Lake Tesse over a period of at least 2300 years, and the results of this early environmental management can still be harvested by sport fishers and professional fishermen today.
In conclusion, the stationary fish traps constructed and maintained in the mountain lake Tesse during the Mesolithic (c. 5000 BC) and the Neolithic (c. 3850–2700 BC), together with other archaeological data such as fish-bone assemblages from settlements around other central Norwegian mountain lakes, provide evidence of a deliberate and well-planned ecological intervention by the region’s hunter-fisher-gatherers. Brown trout were introduced to previously fishless lakes and later harvested. Such a documented practice offers new insights into how past populations were actively involved in permanently shaping future environments and human societies.
Acknowledgements
We would like to express our gratitude to Reidar Marstein for his commitment to the search for archaeological heritage in the Norwegian mountains and for reporting the discovery of the fish traps at Lake Tesse in 2022. We also extend our thanks to Espen Finstad and Fredrik Bratlie Hansen from Innlandet County Council, as well as Morten Reitan and Elling Wammer from the Norwegian Maritime Museum, for their invaluable support throughout various stages of the project. Thanks also to Björn Gunnarson at Stockholm University for use of his tree-ring data from Jämtland, Sweden, and to John F. Smedstad Moore for his careful proofreading of the manuscript. ChatGPT was used exclusively for the language revision of early versions of the manuscript.
Funding statement
The excavation project was funded by the Norwegian Directorate for Cultural Heritage as part of the Sector fee for the examination of cultural heritage sites in regulated watercourses.
Online supplementary material (OSM)
To view supplementary material for this article, please visit https://doi.org/10.15184/aqy.2026.10392 and select the supplementary materials tab.
Author contributions: CRediT categories
Axel Mjærum: Conceptualization-Lead, Data curation-Supporting, Formal analysis-Lead, Funding acquisition-Lead, Investigation-Equal, Methodology-Equal, Project administration-Lead, Resources-Lead, Validation-Equal, Visualization-Equal, Writing - original draft-Lead, Writing - review & editing-Lead. Ellen K. Friis: Data curation-Equal, Formal analysis-Equal, Investigation-Lead, Methodology-Equal, Project administration-Supporting, Validation-Equal, Visualization-Equal, Writing - original draft-Supporting. Trygve Hesthagen: Conceptualization-Supporting, Investigation-Supporting, Validation-Equal, Writing - review & editing-Supporting. Andreas J. Kirchhefer: Conceptualization-Supporting, Data curation-Equal, Formal analysis-Equal, Investigation-Equal, Methodology-Equal, Software-Supporting, Validation-Equal, Visualization-Equal, Writing - original draft-Supporting.
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