- Cleaner fish are a unique group of fish species known for their mutualistic behavior of removing parasites, dead skin, and debris from the bodies of other fish, known as “clients.” This symbiotic relationship benefits both the cleaner and the client: the cleaner fish receive a source of food, while the clients enjoy improved health and hygiene.
- Cleaner fish are most famously found in coral reef ecosystems, where biodiversity is high and the opportunity for such interactions is abundant.
- One of the best-known cleaner fish species is the bluestreak cleaner wrasse (Labroides dimidiatus), which inhabits coral reefs in the Indian and Pacific Oceans. These fish set up “cleaning stations” where larger fish voluntarily come and pose, often opening their mouths and gill covers to allow the cleaner wrasse access to hard-to-reach areas. Remarkably, this behavior is cooperative and often involves intricate communication and trust between species that would otherwise have a predator-prey relationship.
- Cleaner fish have evolved several adaptations that facilitate their role. These include bright coloration and distinctive markings, which make them easily recognizable to client fish, as well as specialized mouthparts that allow them to pick parasites and debris from the skin, gills, and mouths of other fish. Their behavior is also highly ritualized; they perform a characteristic “dance” to signal their readiness to clean, which helps avoid being mistaken for prey.
- The cleaner-client relationship is a prime example of mutualism, a form of symbiosis in which both species benefit. This interaction has also been observed to influence the health of reef communities, as cleaner fish help maintain the well-being of numerous reef species. In the absence of cleaner fish, parasitic infestations can increase dramatically, potentially affecting fish populations and the overall health of the reef.
- Beyond their ecological role, cleaner fish have practical applications in aquaculture. Certain species, such as the lumpfish (Cyclopterus lumpus) and ballan wrasse (Labrus bergylta), are used in salmon farming to control sea lice infestations naturally, reducing the need for chemical treatments. This has made cleaner fish an important tool in sustainable fish farming practices.
