Methodological bias in home range and mobility estimates when locating radio-tagged trout, Salmo trutta, at different time intervals

University of Liège, Laboratory of Fish Demography and Aquaculture, 10 chemin de la justice, B-4500 Tihange, Belgium

Received: 7 April 2000
Accepted: 11 October 2000

Abstract

Radio tracking has been extensively used to enhance our knowledge on the movement and home range of fish in general and salmonids in particular. However, the use of various temporal sampling protocols is likely to overlook fish movements, and produce experimental artefacts, the amplitude of which is unknown and may compromise comparison of fish behaviours revealed by different protocols. Starting from a day-by-day tracking study of brown trout in Belgian waters (Aisne stream, nine fish, minimum 39 daily locations per fish), we re-examined their home range and mobility, through a subsampling process, as if the fish had been located at longer time intervals (2–14 days). The estimates from subsamples were compared to the original data set in order to quantify the corresponding reduction of accuracy from observed data, and how far this could be predicted on the basis of locating frequency. The results clearly indicate that all intervals longer than one day generally generate substantial biases (reduction of accuracy from 0 to 82% for home range and from 5 to 92% for mobility) but these can be partly corrected through the use of predictive models. This analysis demonstrates that any comparison between studies relying on different locating frequencies can generate some ambiguity when interpreting biological phenomena or geographical differences.