Growth, behaviour and colour changes of juvenile King George whiting (Sillaginodes punctata) mediated by light intensities

Light is an important environmental factor regulating physiological processes and ecological activities in fishes. This research aimed to examine the effect of light on the growth, distribution and body colour of juvenile King George whiting (Sillaginodes punctata) when fish were exposed to different light levels under laboratory conditions. In this study, the fish were exposed to three light levels (25, 500, and 1000 lux) in triplicate for two months. Comparisons were made for growth, body colour and behavioural changes between treatments. During the experimental period, there were no statistical differences in specific growth rate, survival, growth efficiency and condition factor between the light levels. Although light did not affect swimming speed or encounter rates, it did influence group flight activity and fish distribution in the tanks. Whiting in low light preferred to spend more time grouped at the bottom of the tank than at medium (500 lux) or high light (1000 lux). Likewise, after having been exposed to low light, whiting exhibited a brighter colour and had fewer body markings and counter-shading than fish in medium and high light intensities. Differences in fish distribution and body colour between medium and high light intensities were not detected. This study offers a new insight into understanding the impact of light on behaviour and body colour of fish, which may contribute to the spatial distribution, predator avoidance and recruitment of fish in inshore coastal waters.