Dive Dry with Dr. Bill

005: Cleaning Symbiosis

Learning about each species of marine life in Catalina waters can be interesting and important in understanding and protecting our ocean. However, it is somewhat like learning the names and backgrounds of the actors who are characters in a play. It is the play itself, the interaction between these actors, that you really came to see. Likewise in the "ecological play" of natural systems, it is the interaction between species that can be spell-binding.

Back in the 1950's underwater pioneer and biologist Conrad Limbaugh observed that certain fish and marine invertebrates picked parasites off the bodies of other fish, obtaining food in the process and relieving the cleaned fish of a potential health threat. He believed this cleaning behavior was not only helpful, but essential to the diversity and health of the ecosystem itself. When Limbaugh removed all the cleaner species from a reef, most of the other fish left and those that remained were in poor health. Although his studies have been questioned in more recent research, Limbaugh brought scientific and popular attention to these interesting interactions.

Symbiosis is an interaction between two species that is beneficial to both. Divers in the Casino Dive Park can easily see an example of "cleaning symbiosis" between the senorita and the very common blacksmith (a close relative of the garibaldi). Tight clusters of the deep-blue blacksmith often surround one or more senoritas which inspect the blacksmith and pick parasites off their bodies. When the senorita finishes and swims off, the cluster breaks apart and the blacksmith often follow the senorita trying to attract more attention.

Senoritas are members of the wrasse family, a group that includes many cleaner fish throughout temperate and tropical waters. Wrasses have pointed snouts with tweezer-like mouths well-shaped for picking small invertebrates off rocks, kelp blades and other fish.

The rock wrasse was not known to be a significant cleaner species in southern California. Recently, only one documented incident of a rock wrasse cleaning other species was noted by a fish authority. I have observed numerous occasions in the Dive Park, especially over the sandy bottom to the northeast, where rock wrasse have cleaned halfmoon (or Catalina perch) as in the photo above. You can witness this by locating groups of halfmoon swimming close together near the bottom. I have also seen rock wrasse cleaning individual garibaldi in mid-water.

Other cleaning interactions observed in our waters include senorita cleaning garibaldi, halfmoon, giant kelpfish, topsmelt and even huge black sea bass; kelp surfperch cleaning kelp bass and small black perch; perch cleaning blacksmith; and opaleye cleaning topsmelt.

Many cleaner species establish "cleaning stations," locations on the rocky (or coral) reef where other fish know to find them. Different species may enter the station, and wait their turn to be cleaned. Sometimes fish "solicit" cleaning from a cleaner species by adopting a specific posture in the water column. Some remain still vertically with their head or tail down, while others stay horizontal, wavering their dorsal and ventral fins.

The most interesting example of cleaning solicitation I'm aware of was observed by one of my students at the former Catalina Island School for Boys in the early 70's. A large ocean sunfish (Mola) came to the surface and began flapping its dorsal fin to-and-fro on the water. This signal attracted a Heerman's gull which came down and began picking parasites off the sunfish's fins for several minutes. The interaction was observed several times, and was later reported by others as well.

© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Image caption: Female rock wrasse cleaning halfmoon on bottom

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia