An individual of Choerodon schoenleinii was photographed on the Southern Great Barrier Reef carefully positioning a clam in its mouth to smash against a rock. By Jane Goodall’s definition of tool use this tuskfish was definitely using an “external object as a functional extension of mouth or hand in the attainment of an immediate goal“. Aquarium keepers of large Coris, Halichoeres and tuskfish will not be surprised at all to learn that a large tuskfish was seen smashing clams against rocks, but perhaps a little befuddled that scientists recently made a big deal about it since large aquarium wrasses regularly smash feeder fish and crustaceans to get at the meat inside.
What is perhaps more fascinating to us is that four of the six photographs published on this event in Coral Reefs feature angelfish in the frame, perhaps indicating tool use by another group of fish. The divers who documented the clam-smashing tuskfish reported seeing many opened shells in the vicinity and the Chaetodontoplus angelfish know what’s up. In much the same way that the tuskfish is using the exposed rock as an anvil to open its clams, it’s highly probable that some scribbled and queensland yellowtail angelfish are aware of the routine and using the tuskfish as a delivery service for clams on the half shell.
[Coral Reefs via Io9]
