PHYSIOLOGICAL AND BEHAVIORAL-STUDIES ON T HE STIMULATING EFFECT OF STROBE LIGHT .1. AVOIDANCE-RESPONSE OF JACK MACKEREL TO A STROBE LIGHT BARRIER

The avoidance response of the jack mackerel Trachurus japonicus to a s trobe light barrier was investigated in the laboratory, by electrocard iogram measurement. The avoidance response varied with the strobe flas h frequency (1.7-430 Hz) and strobe light intensity. Avoidance was gre atest at flash frequencies of 5 and 10 Hz and clearly decreased as the strobe light intensity (15 1x . 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 barrie r or strobe light. Therefore, heart rate change can be used as an inde x of fish response to the effect of strobe light stimuli.