Abstract:

The photogradient method was used to study the dynamic phototaxis behaviors of Blue tilapia (Oreochromis aureus) during four groups divided by different growth stages:Ⅰ: 20.0-50.0 mm, Ⅱ: 50.0-80.0 mm, Ⅲ: 80.0-110.0 mm, Ⅳ: 110.0-140.0 mm, which was exposed to the white lights at five intensities 250 lx, 500 lx, 1000 lx, 1500 lx and 2000 lx, in order to understand the regular behavior of Blue tilapia in optical field. Furthermore, the behavioral response of Ⅰgroup under four different wavelength lights (red, yellow, green, blue) was discussed. The results showed that under the white light four groups of Blue tilapia behave positive phototaxis. The phototaxis index of four groups increased with the boosted light intensity which the range was 250-1000 lx, then decreased with the boosted light intensity when 1000-2000 lx. The phototaxis index reached the maximum when the light intensity was 1000 lx, which were 67.5%, 55.0%, 55.0% and 42.0% respectively in high light district. The total phototaxis indexes of four groups were 96.0%, 94.0%, 96.5% and 95.0% respectively. Blue tilapia preferred light intensity between 500-1500 lx. The phototaxis index decreased with the development of Blue tilapia, and the maximum phototaxis index rank was Ⅰ>Ⅱ>Ⅲ>Ⅳ. Otherwise, Blue tilapia of Ⅰgroup performed differently in four color lights. It preferred blue and green lights to red and yellow lights. It was concluded that Blue tilapia behaved selectively in different light intensity, different wavelength lights and at different growth stages. The results could be used for developing trapping light equipments and improving benefits of industrial culture.