Mobility and year-round habitat use (depth and temperature regime) of Lake Saimaa Arctic Char will be surveyed beginning from 2023 with acoustic telemetry of adult fish that are caught for collection of eggs and sperm for maintenance of the hatchery-reared broodstock of the critically endangered population. The fish are tagged before their release back to their natural habitat in lakes Saimaa and Kuolimo, and their possible movements between major water areas separated by straits and archipelagoes are recorded.