Fig. 4
Heart rate (fH, bpm), external acceleration (EA, mg), variation in EA (VAR, mg2) and temperature (°C) data in free-swimming Atlantic salmon (n = 10) for 1 week following surgical implantation of centi-HRT ACT tags (a), and for 6 weeks at 8 °C (b; n = 5) and 8–12 °C (c; n = 5) after implantation. Fish were on a 12 h light:12 h dark photoperiod (gray bars represent periods of darkness/night-time), and data were collected at 10-min intervals in a, and every 2 h in b and c. Temperature varied in c due to issues with facility temperature control