Published online by Cambridge University Press: 05 December 2011
The patterns of movements of indigenous and displaced trout (Salmo trutta) in a small loch were obtained by ultrasonic tracking techniques. Comparisons of these were made by developing stochastic simulations of their movements based on an analysis of the frequency distributions of step lengths, angles of turn and the percentage time spent actively swimming.
The dispersal and escape of displaced fish from an unfamiliar area of the loch can be explained principally in terms of random turning. Nose plugging appears to influence the distribution of the angles of turn without significantly altering the time taken to escape and return home.
Indigenous trout show a strong preference for turns of 180°, indicating a tendency to turn in their tracks. Although a simulation of the indigenous fish shows slower dispersion than displaced fish, it is insufficient to explain the containment of movement within a home range. It is probable that successive steps are not independent and there may be some association between step lengths and subsequent angles of turn. The implications of their autocorrelation are discussed.
This paper was assisted in publication by a grant from the Carnegie Trust for the Universities of Scotland