The false cleanerfish relies on aggressive mimicry to bite fish fins when benthic foods are scarce in their local habitat.

The false cleanerfish, Aspidontus taeniatus (Blenniidae), is known for its morphological resemblance to the bluestreak cleaner wrasse Labroides dimidiatus (Labridae). It has been suggested that A. taeniatus, which acts as a mimic, can easily bite the fins of other fishes that are deceived into requesting cleaning from it or allowing it to approach them. In fact, A. taeniatus frequently utilises benthic food items, such as damselfish eggs, the Christmas tree worm Spirobranchus giganteus, and the boring clam Tridacna crocea. Although geographical variation in the reliance on aggressive mimicry (fin biting) has been reported, the factors have not been determined. We hypothesised that one of the factors is the abundance of benthic food items. To examine our hypothesis, we compared the feeding behaviour of A. taeniatus at two locations showing contrasting abundances of benthic food items in Okinawa, southern Japan. The frequency of fin biting by the small A. taeniatus in Ishigaki Island, where S. giganteus and T. crocea were very rare, was significantly higher than that in Sesoko Island, where the two food items were abundant. We conclude that the importance of aggressive mimicry in A. taeniatus varies depending on local food conditions.