Movements and habitat preference of adult rainbow trout (Oncorhynchus mykiss) in a New Zealand montane lake

Abstract

Adult rainbow trout (Oncorhynchus mykiss) in Lake Coleridge were tagged with ultrasonic transmitters in 1992, and tracked for up to a year to determine movements, and spatial and temporal changes in habitat preference. Three types of movement were identified: wide-ranging covering much of the lake, localised within the littoral, and migratory towards river mouths before spawning. Maximum swimming speeds up to 2.27 km h−1 were observed, and speeds of 0.5 km h−1 over several hours were recorded for two fish tracked in the limnetic zone. Adult rainbow trout inhabited littoral areas through winter and spring, with most shifting to a limnetic habitat in summer and early autumn. We suggest that the wide-ranging limnetic lifestyle is in response to opportunities for feeding on ichthyoplankton, notably larval bullies and galaxiids. Some individuals remained in littoral areas throughout the year, apparently having adopted a benthic/nearshore feeding strategy. As winter approached several fish moved towards the mouths of inflowing streams, before undertaking spawning migrations. © The Royal Society of New Zealand 1995.