Why are reef fish so colorful?

Reef fishes have evolved some of the most amazing color patterns in the animal kingdom and no family holds more species with chromatically intense, out of this world designs than the wrasses.

With over 600 species, wrasses are the most abundant, conspicuous fishes on the reef. It is no wonder that these small, missile-shaped gems are cherished by divers and aquarium hobbyists around the world.

The purpose of color underwater reaches far beyond a pretty face. In fact, fish see color much differently than we do. What appears bright to us may not be bright to fish — especially at different depths, against different backgrounds in the reef structure and without artificial light, such as strobes. Wrasses  use their coloration in several different ways:

Camouflage

Wrasse often patrol the reef looking for food and use their complex color patterns to blend into the background, thereby avoiding predators. Their markings and streaks break up their outline, size and shape, which make them difficult to locate.

Tailspot Wrasse (Halichoeres richmondi).

Exquisite Wrasse (Cirrhilabrus exquisitus).

This juvenile Rockmover Wrasse (Novaculichthys taeniourus) resembles algae and mimics the movements of detached, drifting seaweed by swaying back and forth in the currents.

The orange and green/blue colors of this Christmas Wrasse (Thalassoma trilobatum) combine in the distance due to the poor spacial resolving power of fish. The resulting color closely matches the blue background, hiding the fish from potential predators.

Species Recognition

Wrasses are very mobile and have large territories. Color patterns help them find their mates, minimizing aggression and conserving energy.

Two wrasses retreat into hiding at dusk (Indonesia). The different color pattern of this male blue-sided wrasse (below) and male filamented flasher wrasse help them tell each other apart.

The matching color pattern of these male Orangeback wrasses help them recognize each other.

Show Dominance

Reef fishes use color to define territories and show dominance. Dominant wrasse males are always larger and often more colorful than females. In fact, color differences are sometimes so extreme between sexes that scientists believed them to be separate species.

A male Orangeback Wrasse (Cirrhilabrus lubbocki) oversees its harem of females.

Attract Mates

Useful in deception and identification, color can also speak the language of love for reef fishes. In many wrasses, the males can intensify their colors or change patterns rapidly when displaying to females or to other males. Flasher wrasses are named after their grandeur “flashing” behavior during courtship. To attract a mate the male undergoes exaggerated lateral moves while intensifying his colors and erecting his fins “flashing” the females.

A male Blue Flasher Wrasse (Paracheilinus cyaneus). Flasher wrasses are named after their grandeur “flashing” behavior during courtship. To attract a mate the male undergoes exaggerated lateral moves while intensifying his colors and erecting his fins “flashing” the females.

A male Blue Flasher Wrasse (Paracheilinus cyaneus) up close.

Advertise Cleaning Services

Color and body pattern are important in signaling cleaning services to coral reef fish. The dark median horizontal stripe on the body identify cleaner wrasses (Labroides sp.) to their host.

Bluestreak Cleaner Wrasse (Labroides dimidatus) at a cleaning station tending to blue streak fusiliers (Pterocaesio tile).

Two Bluestreak Cleaner Wrasse (Labroides dimidatus) tend to a Bluestreak Fusilier (Pterocaesio tile) (Indonesia)

A Hawaiian cleaner wrasse picking dead skin and parasites off a Longnose Butterflyfish (Hawaii).

Labroides species are not the only wrasses that provide parasite removal services. Here a Spanish hogfish (Bodianus rufus) cleans a spiny balloonfish (Diodon holocanthus).

Mimic other Fishes

Mimic species have color patterns that imitate other species to gain a competitive advantage.

The Potters Wrasse mimics the Potters Angelfish – a larger, more spiny, harder to catch fish.

Potter’s Angelfish (Centropyge potteri), a species endemic to the Hawaiian Islands.

NO CORAL REEFS   —  NO COLORFUL REEF LIFE

Coral reefs are biological treasures. They support a quarter of marine life on the planet and are a vital human food source.

But roughly 20% are damaged beyond repair with another two-thirds under serious threat — mostly due to diseases, coastal pollution and development, destructive fishing practices and warming oceans.

If reefs continue to deteriorate, reef animals won’t be able to hide or find one another. Instead of complex backgrounds, brightly colored fish would live on plain backgrounds — much like deer feeding on a meadow but without a forest to hide in. Natural selection would favor less colorful reef animals and those that don’t depend on corals for food or shelter.

It’s not all doom and gloom. Certain corals are surviving better than others. Scientists are working to identify what helps these corals tolerate stress and recover more easily. Corals could be conditioned or condition themselves to survive in altered oceans. Stress resistant strains could also be developed and used to recolonize damaged reefs. Local efforts play a central role in keeping corals healthy enough to adapt to climate change. These include:

1. Reducing pollution and coastal development.
2. Protecting the alage-eating fish, such a parrotfishes that keep seaweed from smothering corals.
3. Stopping destructive fishing practices, like the use of dynamite and poisonous chemicals.

Wrasses, with their myriad of color patterns, are  wonders of evolution…

A collection of my favorite wrasse photos