Abstract
Blinking frequencies and contrast ratios between bright and dark light intensities of inter-mittent lights for which a school of fish had the most prominent hatred and those for which the school did not show any dislike were studied from an ecological point of view in this report. Jap-anese horse-mackerel Trachuras japonicus were used soon after being caught by a stationary trap net for the experiments. The observations of the fish school's behavior in response to the intermittent lights which have different blinking frequencies and contrast ratios between bright and dark light intensities were continuously carried on for a period of 70 days, during which ex-perimental fish were replaced with new ones everyday. Total number of fish used for the study amounted to 1, 050.
As a result, it is concluded that the most hateful blinking frequencies of intermittent lights for the school are in the region of 1.36 c/s to 0.62 c/s; that the intermittent lights having such contrast ratios as more than 60:1 are confirmed to exert a prominent effect on behavior of the school of fish, but such effect disappears in the case of the ratio 2:1.
