First record of a grouper (Epinephelus costae) acting as a cleaner of sea turtle (Caretta caretta): an unusual interaction on Mediterranean reefs

Abstract

Cleaning associations between sea turtles and fish are a widespread interaction in which small herbivorous and invertivorous fishes act as cleaners (Sazima et al. 2010). Large piscivorous species are mostly recorded as clients, and, to date, groupers have never been recorded as cleaners (sensu Cote 2000 and Sazima et al. 2010). Here, we present the first record of the goldblotch grouper (Epinephelus costae), a mostly piscivorous reef fish, engaged in an opportunistic cleaning event with the loggerhead turtle (Caretta caretta). The interaction took place on a rocky reef in the southwestern Mediterranean Sea, at Cabo de Palos-Islas Hormigas Marine Reserve, in November 2012, and lasted about 3 min. The sea turtle of approximated 70 cm (carapace length) arrived at the reef from open waters, accompanied by three juvenile pilot fish (Naucrates ductor) of 3–7 cm in total length that hovered above its head (Fig. 1a). The turtle had goose barnacles (Lepas sp.) growing on its carapace (∼80 individuals) and hind flippers (∼20 individuals). Closer to the rocky bottom at 20 m depth, the turtle searched for cleaners during the first minute, identified by its postural behavior (Sazima et al. 2010), when it approached a goldbotch grouper (E. costae about 60 cm long; Fig. 1b). The grouper perceived the turtle and swam quickly towards it, firstly preying upon the pilot fishes (Fig. 1c), and after performing a few turns, the grouper removed some of the barnacles on the carapace and flippers (Fig. 1d); the feeding and cleaning actions took about 2 min. Serranids are known as versatile and opportunistic hunters (Randall 1967), thus, through this cleaning association with a turtle, E. costae was able to feed on otherwise inaccessible prey. Although the interaction benefits both cleaner and client, the protective role of the turtle for the pilot fish was overcome by the grouper, as these were promptly preyed by this piscivorous fish. C. W. Hackradt : F. C. Felix-Hackradt (*) Department of Ecology and Hydrology, University of Murcia, Murcia, Spain e-mail: felixfabianac@gmail.com