Effects of different wavelength lights on growth of rock bream (Oplegnathus fasciatus)

Abstract

In aquatic environment, light is one of the important environmental factors, which can affect physiological processes such as growth, behavior and development in fish. In order to examine the effect of different wavelengths of light on fish, growth performance and physiological aspects such as hematology and histology of fish grown under different wavelength of light by using LEDs (fluorescent light for control group) were tested for rock bream (Oplegnathus fasciatus). Fish were grown under illuminations of LEDs with wavelengths of 400 nm (Violet), 462.5 nm (Blue), 507.5 nm (Green), 590 nm (Yellow) and 635 nm (Red), together with a white fluorescent light control for 50 days. The result showed that weight gains and specific growth rates of the fish reared under green LED illumination were significantly higher (P <0.05) than those of other groups. While the level of cortisol in the fish grown under green LED illumination was significantly lower than other groups (P<0.05), their levels in fish grown under violet and red LED were significantly higher than that of the control group. Histological analysis of the retina indicated no significant difference in the ratio of photoreceptor layer thickness to that of the total retinal layer thickness amongst groups. The result suggests that little, if any, adverse effect of the green LED illumination on the retina, one of the most light-sensitive tissues in fish. Spectral analysis of the visual pigments in rock bream eyes revealed presence of the photoreceptors with absorption maxima of 500±1.5 nm in rod cell, and 452±1.5 nm, 490±1.9 nm, 536±1.5 nm and 595±1.4 nm in cone cells.