Pattern of movements of adult Barbus haasi in a small Mediterranean stream

Most adult Barbus haasi, at a 1950 m-long site in Vallvidrera creek, were h ighly sedentary and resided within a home rang <20m (32 m(2)), while a smal l group were more mobile. On successive sampling occasions, between 52.3 an d 64.9% of fish were recaptured in the same 10-m-long section in which they had previously been captured. Movements over long distances were infrequen t, and only 5.6% of the fish moved >100 m. The movement pattern of the popu lation was seasonally stable, although the mean distances were slightly gre ater in summer because of the medium-range movements of a few individuals. Overall, upstream and downstream movements were equally common but a signif icant downstream movement occurred in spring. The size of the fish did not influence the movement rate. Fish inhabiting those sections of the stream w ith greater depth, slower current and more cover had a lower movement rate than fish occupying shallower, exposed sections. The restricted movement of B. haasi could increase the survival of fish by increasing the probability of staying in the remaining pools during summer dry-out, and may therefore be of adaptive significance. (C) 1999 The Fisheries Society or the British Isles.