DEVELOPMENT OF PORTABLE SYSTEM FOR MUSCLE TWITCH EXPERIMENT MEASUREMENT OF MUSCLE CONTRACTION TIME

The muscle contraction time of fish can be the good index for swimming capability to estimate the maximum swimming speed, by defining the maximum tail beating performance. The muscle contraction time of jack mackerel, Thachurus japonicus (18.0 – 19.4 cm of fork length (FL), n = 15) was measured with newly developed portable systemand compared with the conventional setup with the electric stimulation pulse from generator and battery system.The muscle contraction profile was not different among each measurementeven with the different pulse pattern of electric stimulation between portable and conventional setup. The shortest recording of muscle contraction time with the portable system was 22.6 ± 2.1 ms, not different to the conventional system as 24.3 ± 1.9 ms with the generator and 24.2 ± 2.0 mswith the battery system. Time duration and the pulse pattern of the electric stimulus do not affect the muscle contraction time. The portable system can be used to measure the muscle contraction time of fish for the field experiment and onboard the fishing boat without alternating current (AC) electricity supply. Keywords: Muscle contraction time, jack mackerel, portable system, electric stimulus, muscle twitch experiment.