1Faculty of Fisheries, Kagoshima University, Kagoshima 890-0056, 2Excel-Kyoto Inc., Kyoto 602-8453, Japan
This study examined the effectiveness of E-LEDs flicker lights on invasion by the red sea bream Pagrus major in an indoor tank. The E-LEDs used were blue, green, red and UV and they were modified to diffuse emitted light. Flicker frequency and irradiance were varied from 0.3 to 20 Hz and 0.656 to 806 μW cm−2 by operating a control unit. The fish had been trained to repeatedly pass through an open gate surrounded by E-LEDs, and then the flicker lights were applied during tests. The number of fish that passed through the open gate during controls (no flicker light) and tests was videotaped and counted, and the anti-invasion effectiveness indices were computed. The fish showed remarkable aversive responses to the blue, green and red lights but not to UV. The anti-invasion effectiveness was highest for the blue and green lights. The highest effectiveness was obtained at flicker frequencies ranging from 1 to 10 Hz. The low effectiveness of UV was attributed to the lack of UV cones in the retina of the red sea bream, while UV perception was possibly achieved by blue cones that had a slight UV sensitivity.