The catfish were released on 10th October 2010. The first three weeks of their activity were
not analysed due to the possible impact of the implantation on the fish’s spatial and temporal
activity (Bridger and Booth, 2003). The tracking therefore started on 2nd November. The
last data analysed were from 1st February. The fish were tracked on a weekly basis, always
for a 24-h period. Fish positions during the 24-h cycle were determined by triangulation at
eight subsequent three-hour intervals. A radio receiver SRX 400A/W5XS and a three-element
Yagi antenna F 140-3FB (Lotek Engineering Inc., Newmarket, Ontario, Canada) were used for
tracking. The accuracy of the fish position determination was estimated to be ±1 m according
to a calibration procedure repeatedly performed with a tag located on the lake bed (n = 100;
mean = 0.74 m; min = 0 m; max = 3.2 m).