Beauty Is In The Eye Of The Beholder: How Fish Use Their Colors

Of all the creatures living in the sea, fish are perhaps the most exquisite in terms of color variation. We enjoy watching them, artists pay homage to them by creating stunning images based on their likenesses, and their shapes inspire engineers to create more efficient machines. Our fascination with fish isn’t off-base; in fact, these creatures use their colors and patterns to attract mates, as well as for other functions. How do they do it? Let’s take a closer look. 

How Fish Perceive Color

The human eye is only capable of perceiving a certain portion of the color spectrum, particularly after water absorbs the reds, oranges, yellows, and greens, leaving only blue colors behind. Yet fish and other marine animals exhibit an endless array of color variation, which led scientists to believe that many of these creatures must have the ability to see colors we cannot perceive while underwater. 

Tests have proven that fish eyes are sensitive not only to colors we humans can perceive, but that they are actually sensitive to a much broader spectrum. In fact, they are even able to perceive colors revealed under ultraviolet light, which penetrates much more deeply into the water than do the shorter light waves we are able to see. So, even though humans cannot see much color underwater without the help of bright dive lights, fish are perfectly capable of recognizing color and using it in a number of intelligent and innovative ways. 

Encryption 

Different fish perceive colors differently, particularly when color variations exist among members of their own species. Some fish change their colors to attract mates, aiding in effective reproduction and ensuring that fertile fish find one another easily, even when swimming with a diverse group of similar-looking schoolmates.

In many fish species, males are one color and females are another, as is so often the case among birds and some other animals. In others, juveniles look different than adults; for example, adolescent garibaldis have distinct blue spots on their bodies, which show that they have not yet reached maturity. These features serve to make searching for a spawning partner easier and more efficient – fish are only attracted to compatible mates.

Blending and Merging

Color coding isn’t always just for signaling readiness to mate or for telling one gender from the other. Many fish use their colors to blend in with their surroundings, making fooling potential predators simple and facilitating easy escape.

Turbot and peacock flounder are two fish species which are masters of disguise. When on the seabed, they are able to change colors and patterns to better blend in with their surroundings. This happens almost instantly and is achieved via specialized pigment cells. 

Virtual Shape

Some fish species are able to alter their colors in a way that makes gauging the fish’s body structure and size difficult for potential predators. This tactic causes confusion and aids in easy escape, and is referred to as disruptive coloration. 

Fishes exhibiting disruptive coloration are often striped horizontally or banded vertically. Some fish are able to change colors and patterns, switching between stripes and bands to fool predators even more. Some angelfishes are capable of evading predation using this tactic. 

 Another way some fish use colors and stripes is to disorient predators. Have you ever noticed that some fish have stripes that cut through their eyes, often with identical stripes to the rear? These stripes confuse would-be predators, causing them difficulty in determining which direction the fish is likely to head in. Without the ability to tell head from tail, predators are less likely to catch the fish they prey upon. 

The four-eye butterfly fish takes the art of anatomical disguise to a completely new level, thanks to spots on its tail which are nearly identical to the spots around the fish’s eyes. Predators have a 50/50 chance of determining which direction these fish will go, boosting the fish’s chance of survival by fifty percent. 

Cleanup Act

Barracudas often prey on small fish, but on occasion, they call a truce and request cleaner fish and shrimp to remove parasites from their bodies. They do this by changing color to highlight the presence of parasites. During the cleaning process, their body color changes even more dramatically, showing an even greater contrast between their skin and the parasites they need to have removed. 

Word of Caution

Some fish use bright colors to warn others that they’re not safe to eat. For example, lionfish transform themselves with vivid hues when predators are near, providing them with a courteous warning concerning the presence of the lionfish’s sharp, venomous spines. 

Stingrays and barjacks interact in a similar way, but these animals convey a different message to one another. As both species prefer the same type of food, barjacks warn stingrays away while eating. These fish are usually silver in color, but they change to black when eating, signaling the rays to back off. Once they’re finished feeding and it’s safe for the rays to move in, the barjacks return to their original silver hue. 

Countershading

Many species use contrasting shades called countershading, which often makes it difficult for others to spot them. Not only does countershading serve as a method for evading predation, it also serves as a method for ambushing prey by hiding in plain sight. Animals that employ countershading have dark dorsal sides and light colored ventral sides (undersides). When viewed from below, these animals blend in with the lighter color at the surface; when viewed from above, they blend in with the dark-colored water and seabed beneath them. Many sharks use this tactic, as do rays and tiny surface-level fish such as halfbeaks. 

As divers, we are privileged to see these amazing creatures in their natural habitats and witness the many ways in which they use color to their advantage. Without a doubt, we have even more to learn from these fish; colors and patterns are only the tip of the iceberg.