Fig. 5
Average day-time and night-time heart rate (fH in bpm; a), percentage of ‘good’ quality ECG values (i.e., QI0; b) and external acceleration (EA in mg; c) values in free-swimming Atlantic salmon (n = 10) recorded for 7 days following surgical implantation of the centi-HRT ACT tag. Open symbols represent day-time, whereas dark symbols represent periods of darkness/night-time. Dissimilar lower case letters indicate a significant difference within photoperiod (night-time values in bold), while an asterisk (*) represents a significance difference between day-time and night-time values at each measurement period. Data are means ± S.E.M, with each value representing the average of n = 72 data points per fish