Mixedschooling and its possible significance in a tropical western Atlantic parrotfish and surgeonfish

Schools of blue tang (Acanthurus coeruleus) are a regular feature of shallow reef fish communities in the tropical western Atlantic. Amember of the herbivorous surgeon fish family (Acanthuridaw), A. coeruleus is one of the most abundant reef dwellers in many areas. While it is not unusual for a few individuals of certain other fish species residing on the reefs to briefly accompany blue tang schools, the midnight parrotfish (Scarus coelestinus) frequently schools with the blue tang for extended periods, and even feeds with it. The midnight parrotfish is also herbivorous, and eats many of the same algae that are prominent in the diet of the blue tang (Randall, 1967). In this paper, I describe mixed schooling behavior in these two species and cite evidence suggesting why the relationship may be especially importnat to the midnight parrotfish.