Fish Uses Tool to Crush Clams

Orange-dotted tuskfish on video uses rock as an avil

First known video of fish using a tool taken in Palau

Similar behavior seen in California

In recent years, there have been several reports of divers witnessing wrasse using a rock as an anvil to crush shellfish. Now - for the first time, there is video proof of this remarkable behavior taken in Palau. In addition, a video has surfaced in Southern California documenting similar behavior in a different wrasse species. 

In the Palau video, an orange-dotted tuskfish, Choerodon anchorago, digs a clam out of the sand in shallow water, carries it over to a rock, and repeatedly throws the clam against the rock to crush it. Giacomo Bernardi, professor of ecology and evolutionary biology at the University of California, Santa Cruz, shot the video in Palau in 2009. The behavior was observed three different times over a course of 20 minutes.

"What the movie shows is very interesting. The animal excavates sand to get the shell out, then swims for a long time to find an appropriate area where it can crack the shell," Bernardi said. "It requires a lot of forward thinking, because there are a number of steps involved. For a fish, it's a pretty big deal."

"Wrasses are very inquisitive animals," Bernardi said. "They are all carnivorous, and they are very sensitive to smell and vision."

Bernardi, who studies fish genetics, said there may be other examples of tool use in fish that have not yet been observed. "We don't spend that much time underwater observing fishes," he said. "It may be that all wrasses do this. It happens really quickly, so it would be easy to miss."

Other Wrasses perform similar behavior

In 1995, a yellowhead wrasse was observed in Florida engaging in similar behavior, and in 2010 a sixbar wrasse was observed in an aquarium setting.

A still photo from Australia has also recently captured this amazing behavior in a wrasse:

First photo taken of a wrasse using a tool to break open a shell. The fish was using a rock as an anvil. Photo by Scott Gardner, taken in the Keppel region of the Great Barrier Reef in November, 2006.

Amazing video showing the wrasse using the rocky reef as an avil, taken in Palau. In the video, the fish first digs up a clam, and then travels quite a ways in order to find a good rock to use to help break open the clam.

Story source

University of California - Santa Cruz. "Fish uses tool to dig up and crush clams." ScienceDaily, 29 Sep. 2011. Web. 29 Sep. 2011.

Journal Reference

    G. Bernardi. The use of tools by wrasses (Labridae). Coral Reefs, 2011; DOI: 10.1007/s00338-011-0823-6. Here is a link to the original paper.

Story photo credit: Image courtesy of University of California - Santa Cruz

Similar Behavior Witnessed in Southern California

In the video above, taken in March 2010, a female sheephead wrasse Semicossyphus pulche is observed trying to break apart a crab by slamming it against a rock.  La Jolla Shores, CA.  Video by Jackie Patay.

Jackie Patay comments on her observation.  "Late morning, I was solo diving the La Jolla Shores [California], along the canyon edge, south of Vallecitos Point. I stopped to hover and watch the behaviors of the various fish.  I observed this female Sheephead continuously picking something up, shaking it like a dog, and repeatedly slamming it against the rocky outcropping.  I came in for a closer look, and caught this little bit of video.  As you can see, she was successful in breaking it apart, and enjoyed her meal.  This was not the first time I saw sheephead do this."

This is an amazing video captured right here in southern California!  Thank you very much for this submission, Jackie.  ~Editor

These still photos and videos show us how much we still have to learn about the intelligence and behavior of the species in our oceans.

Further reading

• Underwater photography in Palau

• Photographing marine life behavior underwater