Influence of Hydropower on Lake Ecology of Atlantic Salmon in a Changing Environment (LakES)

Salmon has a special position in Norwegian culture and is an important connection between people and nature. Atlantic salmon was abundant throughout Europe and Atlantic North America, but the species is disappearing throughout much of its range. Norway is the last stronghold of the salmon, having more than 25% of the remaining populations. Lessons from other countries have emphasized that salmon can disappear quickly and be difficult to restore once lost, so conservation of salmon habitat is a major priority of environmental management. One of the major threats to salmon habitat in Norway is river regulation. Dams and power stations are constructed in hundreds of Norwegian rivers and lakes, which pass water through turbines to generate hydroelectricity. Yet, little is known about how power stations affect lake habitat of salmon. Almost a third of Norwegian salmon rivers include lakes, which are most common features in glacial rivers such as many that we have in Norway. Three work packages have been designed within LaKES to study three life stages of salmon from 2021-2024 in Evanger Lake and Vassbygdi Lake. We will track salmon in the rivers and through the lakes with acoustic telemetry. Acoustic tags for salmon smolts are small and outfitted with predation sensors so that we can map where, when, and under what circumstances smolts are vulnerable to predation. This is particularly key to determine what the ultimate causes of smolt mortality are and whether lakes, and especially hydropower outlets, are hotspots for predation. For adults and kelts, tags with temperature and activity sensors help us determine how lakes are used to modulate the energy budget and whether hydropower outlets, which have different thermal regimes from the ambient water, are used by salmon for thermoregulation. The project aims to provide actionable advice to industry and management as we continue to strive for sustainable energy production and informed policy to protect nature. In 2021, we tagged 90 Atlantic salmon smolts in the river Vosso, 29 return migrant salmon in Vosso, and 31 return migrant sea trout in Aurland. Data were recovered in November 2021, providing nearly 10 million detections of these fish in the rivers and lakes. We have overseen completion of four Masters projects related to LaKES this year, including one defense scheduled for December. Our overview paper "The various ways that anadromous salmonids use lake habitats to complete their life history" was published in Canadian Journal of Fisheries and Aquatic Sciences along with multiple other directly relevant works emanating from the LaKES project. We engaged in an update meeting with the management, industry, and science partners for the project in November 2021 and received positive feedback on project progress. We also received 31 applicants for our PhD position and will complete interviews and hiring shortly. We are on track with our budget and plan for deliverables and are beginning the process of procuring equipment for the 2022 field season. We have planned for international partners to visit in 2022 and received an external scholarship for a 2 month visit from a Canadian PhD researcher to join our summer field work program as a value added opportunity for our research group and student development.

Rivers provide ecosystem services that are crucial to Norway, including potential energy from hydropower and valuable fisheries for Atlantic salmon. Exploitation of rivers for hydropower generation can alter the habitat available to Atlantic salmon by altering water temperature, flow, or chemistry. Many rivers in Norway that are home to Atlantic salmon are connected to large lakes with complex hydrology that salmon must navigate for successful migration, yet, there is a paucity of research on how these habitats are used by salmon. Lakes can be modified by adding new water inlets or outlets that alter temperature/flow or with dams that alter water levels and temperature. Smolts must navigate down through lakes and adults must move up through the lakes to spawning grounds, although some salmon may spawn in lakes where there is adequate flow; after spawning, salmon will overwinter in lakes before moving back to the ocean to recondition. Salmon populations must have adaptations to optimally exploit lake habitat but how hydropower alters this relationship is unknown. The LakES project has partnered researchers from NORCE LFI and Carleton University with three hydropower companies and two management agencies to identify critical knowledge gaps about Atlantic salmon in lake habitats exploited by hydropower around the different life stages of Atlantic salmon that encounter lakes. In the river systems Vosso, Aurlandselva, and Eidfjordvassdraget, we will use acoustic telemetry to observe salmon behaviour in the lakes and rivers. Smolt tags equipped with novel predation sensors and adult/kelt tags incorporating temperature, depth, and activity sensors will provide high resolution insights into how salmon use lakes and the potential impacts of hydropower on these habitats. The project will also support pilot testing of acoustic transmitters with magnetometer sensors, a first of its kind tool for gaining new insights into fish navigation.