This article appeared in the 1986 issue Vol 1. Light, both direct and indirect, is of great importance in the lives of fishes. In the majority of fishes, the visual organs play a substantial role in orientation during swimming, towards prey, predators, other individuals of the same species in a school, or immobile objects. Light exerts a definite influence on a fish's metabolism, maturation, behaviour and colouration. Light conditions in water differ from those on land not only in their intensity but also in the depth of penetration of the various wavelengths.
Light exerts a definite influence on a fish's metabolism, maturation, behaviour and colouration.
Light conditions in water differ from those on land not only in their intensity but also in the depth of penetration of the various wavelengths. Since a high percentage of red light is filtered out in the first few metres of water, bright red fishes are common. In both situations, red light is virtually absent and a red fish tends to fade into the background rather easily. However, many shallow water fish also have red spots or lines. Fish have a number of adaptations to varying light levels.