Fish Color Determines Amount of Received Aggression


Fish can be some of the most colorful and vibrant animals found in nature. Color traits, as we know, is genetically passed down from parent to offspring and through mutations. Sometimes color traits will differ even within the same species of fish. When rarer or new colors are introduced into a species, this creates a “morph”. By studying morphs, biologists have been trying to untangle the mystery of color diversity within the same species and its effect on fish behavior. Recently they’ve uncovered some very interesting insights into how color determines how certain fish within the rarer morphs are treated both by their own species and by other fish in the same environment.

Initially, biologists were studying cichlid fish, which normally appear in either gold or a dark color pattern. Early on researchers saw that the gold cichlid fish were less common than those that had a dark color pattern. This was unusual because the gold cichlids acted like school leaders, being socially dominant over the dark colored fish within the laboratory environment. If this was the case in the wild, evolution would dictate that these fish would also be more prevalent because the more socially dominant color would of course fare better than those that were considered weaker.

The fact that they were rarer was an interesting mystery until they introduced the gold and dark cichlid school to another school of fish called moga, which were also found in the same environment. While the gold coloration proved to be advantageous within the cichlid school, the gold colored cichlids brought out increased aggression in the moga. In fact, gold cichlids were attacked much more than the darker colored cichlids.

Now that the link between color and aggression was firmly established scientists believe that the reason for the increased aggression was due to the fact that the darker cichlids were less noticeable and considered non-threatening. Conversely, gold cichlids were highly visible and considered more threatening than darker patterned fish of the same species. After seeing the behavioral interactions, biologists concluded that color plays a major role in how species are able to survive both within their own species and in interactions with other species. This information will provide valuable data in obtaining a greater understanding of evolution and color heredity between species.

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