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 degrees C, grayling (n=14) stayed mainly in the riffle-section where they were captured in a large regulated river in northern Finland, moving l ittle between consecutive days. In autumn (2-30 October 1998), at 1.7-6.7 d egrees 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 lat e summer and autumn were 54 +/- 32 m (mean +/- s.d.) and 1053 +/- 1636 m, a nd 190 +/- 168 m and 3135 +/- 1850 m, respectively. In autumn the fish used deeper habitats (most suitable range 150-400 cm) with lower current veloci ties (20-80 cm s(-1)) and finer bottom substrata (mainly sand) than in late summer (depth 100-325 cm, velocity 30-110cm s(-1), and cobble-boulder subs trata). (C) 2001 The Fisheries Society of the British Isles.