Seasonal changes in the habitat use and movements of adult European grayling in a large subarctic river

In late summer (13 August-13 September 1998), at water temperatures of 12.0-15.7 degree C, grayling (n=14) stayed mainly in the riffle-section where they were captured in a large regulated river in northern Finland, moving little between consecutive days. In autumn (2-30 October 1998), at 1.7-6.7 degree C, the fish (n=16) migrated to potential overwintering sites 0-14 km up- or downstream by mid October, moving mainly short distances thereafter. The daily movement rates, and the total ranges covered by the fish in late summer and autumn were 54 plus or minus 32 m (mean plus or minus . ) and 1053 plus or minus 1636 m, and 190 plus or minus 168 m and 3135 plus or minus 1850 m, respectively. In autumn the fish used deeper habitats (most suitable range 150-400 cm) with lower current velocities (20-80 cm s super(-1)) and finer bottom substrata (mainly sand) than in late summer (depth 100-325 cm, velocity 30-110 cm s super(-1), and cobble-boulder substrata). Copyright 2001 The Fisheries Society of the British Isles