Cleaner fish

Cleaner fish are fish that show a specialist feeding strategy by providing a service to other species, referred to as clients, by removing dead skin, ectoparasites, and infected tissue from the surface or gill chambers. This example of cleaning symbiosis represents mutualism and cooperation behaviour, an ecological interaction that benefits both parties involved. However, the cleaner fish may consume mucus or tissue, thus creating a form of parasitism called cheating. The client animals are typically fish of a different species, but can also be aquatic reptiles (sea turtles and marine iguana), mammals (manatees and whales), or octopuses. A wide variety of fish including wrasse, cichlids, catfish, pipefish, lumpsuckers, and gobies display cleaning behaviors across the globe in fresh, brackish, and marine waters but specifically concentrated in the tropics due to high parasite density. Similar behaviour is found in other groups of animals, such as cleaner shrimps.

There are two types of cleaner fish, obligate full time cleaners and facultative part time cleaners where different strategies occur based on resources and local abundance of fish. Cleaning behaviour takes place in pelagic waters as well as designated locations called cleaner stations. Cleaner fish interaction durations and memories of reoccurring clients are influenced by the neuroendocrine system of the fish, involving hormones arginine vasotocin, Isotocin and serotonin.

Conspicuous coloration is a method used by some cleaner fish, where they often display a brilliant blue stripe that spans the length of the body. Other species of fish, called mimics, imitate the behavior and phenotype of cleaner fish to gain access to client fish tissue.

The specialized feeding behaviour of cleaner fish has become a valuable resource in salmon aquaculture in Atlantic Canada, Scotland, Iceland and Norway for prevention of sea lice outbreaks which benefits the economy and environment by minimizing the use of chemical delousers. Specifically cultured for this job are lumpfish (Cyclopterus lumpus) and ballan wrasse (Labrus bergeylta). The most common parasites that cleaner fish feed on are gnathiidae and copepod species.

The following is a selection of some of the many marine cleaner species.

Commonly studied cleaner fish are the cleaner wrasse of the genus Labroides found on coral reefs in the Indian Ocean and Pacific Ocean.

Neon gobies of the genera Gobiosoma and Elacatinus provide a cleaning service similar to the cleaner wrasse, though this time on reefs in the Western Atlantic, providing a good example of convergent evolution of the cleaning behaviour.

Lumpfish are utilized as salmonid cleaner fish in aquaculture, but it is unknown if they serve as cleaners on salmon in the wild.