Australasian Science: Australia's authority on science since 1938

Tool Use Observed in Fish

A black spot tuskfish using a rock as an anvil to open a cockle shell. Broken sh

A black spot tuskfish using a rock as an anvil to open a cockle shell. Broken shells are seen lying on the sand near the rock.

By Stephen Luntz

The first clear evidence of tool use in fish has been discovered by chance.

Scott Gardiner, a keen diver who was swimming in the Keppel region, witnessed a black spot tusk fish using a rock as an anvil to break open a cockleshell. He took several photographs.

According to Dr Culum Brown of Macquarie University: “He was running low on oxygen, so we were very lucky to get these shots. He was very excited when he reported them to me, but not as excited as he should have been.”

For a long time tool use was considered a defining trait of humans. However, since Jane Goodall reported it in chimps the use of tools has been observed among dolphins, crows and even octopi. Brown says there has been debate as to whether water can count as a tool, such as when angler fish spit water to knock insects from the air.

Brown says that tool use is a challenge under water, particularly for fish lacking hands. However, the tusk fish in question seized a mollusc in its mouth, moved to a convenient rock and swung its head violently back and forth until the shell broke open.

“When you look at the images it is landing very accurate blows,” Brown says. “It knows exactly where to land the blows, and its head is in perfect condition so obviously it hasn’t hurt itself by missing recently.”

A fish has also been observed in an aquarium using rocks to break open a food pellet designed for larger fish, but Brown says “we didn’t know if it happened in the wild. We really need to spend more time filming underwater to find out just how common tool use is in marine fishes.”

The Great Barrier Reef is strewn with middens where smashed pieces of shell lie, but Brown says “it was always thought these were the result of storms. It’s true you do get fragments of this size after storms, but now that we have seen a fish do this at the site of a midden we wonder whether they might be of biological origin.”

Understandably Brown is keen to return to the site, this time with video cameras to see if the behaviour is unique to a single individual or even a species.

Tusk fish are a species of wrasse common across the Indo Pacific, and are named after their large teeth. Like other wrasse they have complex social structures that may have encouraged the development of intelligence. Brown says he is also keen to test their cognitive skills.