One of the most outstanding features of reef fishes is their remarkable assortment of vibrant colors and variety of patterns. Reef fish use their color for numerous reasons including camouflage for defense, for show, to warn enemies and predators, to attract attention, and to communicate (for example during reproduction). The fish themselves are endowed with well-developed vision and an ability to distinguish colors and color patterns.
Color patterns play an important role in intra-and inter-species communication among reef fish. The huge variety of color patterns testifies to the need for fish to recognize and identify each other in the crowded reef environment. The distinction between males and females and the ability to identify territorial fish are of particular importance.
The relationship between predators and prey among reef fish plays an important evolutionary role in the development of color patterns. It dictated the evolution of patterns for camouflage and masking, unusual color patterns such as horizontal and vertical stripes, lines that conceal the eye, color patterns that imitate the environment, and much more.
In addition, various patterns have evolved for decoration and display, warning colors and patterns with which fish deceive and masquerade. Color patterns may change during the development of certain fish, mainly due to maturation or physiological changes in certain periods of a lifecycle (such as during courtship and reproduction) and to a gender change which is very characteristic among fish. For example the female Randall’s Anthias is orange, and after it changes to a male, its color becomes a purple tint.
An important component of camouflage is the stripes and spots of color that appear on fish. They can highlight or camouflage those parts of the body that are the tell-tale features by which its enemies (or prey, if it is a predator) recognize it. The streaked hoops that appear on coastal fish are to camouflage the fish in shallow waters where the waves break the rays of sunlight, leaving streaks of light and shade on the seabed. Horizontal lines highlight the length dimension of the fish and vertical or contour lines help the fish blend in with the fragmented landscape of the reef.
Fish colors can be divided into two groups: display patterns and camouflage patterns. Camouflage patterns help the fish evade predators while display patterns, or “poster patterns” provide information on the nature of their respective bearers Courtship colors provide information about the reproductive status of a particular fish; in certain species the males and females have different color patterns, enabling each fish to identify its partner.
Lastly, color pattern can serve as a warning. The color pattern of a venomous fish that boldly “shouts” gives enemies a clear message: “Beware, I’m dangerous”. Warning colors are characteristic of toxic or venomous fish such as the poisonous reddish-brown striped turkey fish, the yellow boxfish with black dots, and more.
Masquerading patterns are intended to exploit the color and shape of other fish for the benefit of the masquerader.
A common trick of coral fish is to use eye-like patches. “False eyes” appear on the body of the fish, usually at a considerable distance from the real eye. One explanation for this is that the “false eye” misleads the predator as to the true place of the eye (often hidden by a dark colored band). Another theory is that the “false eye” diverts the attention of biting parasites, attracted to the eye, to less sensitive body parts.