The avoidance response of the jack mackerel Trachurus japonicus to a strobe light barrier was investigated in the laboratory, by electrocardiogram measurement.
The avoidance response varied with the strobe flash frequency (1.7-430 Hz) and strobe light intensity. Avoidance was greatest at flash frequencies of 5 and 10 Hz and clearly decreased as the strobe light intensity (15 Ix•s) was reduced.
Heart rate increased when the fish stayed in the dark section of the tank or approached the barrier, but decreased when fish avoided or passed through the barrier or strobe light. Therefore, heart rate change can be used as an index of fish response to the effect of strobe light stimuli.
