by Steve Reynolds

(STEVE’S SDFSA SCIENCE STORY for the month of September)
According to Hordes of sharks found living in volcano by Raffaella Ciccarelli, reef and hammerhead
sharks are thriving in the explosive crater of Kavachi volcano in the Solomon Islands. (Sharks have
also been found in an active volcano called Piton de la Fournaise at Réunion Island in the Indian

(Photo from video footage taken by David Muirhead)

Kavachi is one of the world’s most active submarine volcanoes. National Geographic’s Dr Brennan
Phillips discovered the sharks there in 2015. This led to a National Geographic documentary titled

Michael Heithaus from Florida International University’s Department of Biological Sciences has since
been studying why the sharks are attracted to the volcano. Water temperatures there reach near boiling point 18 metres below the surface. Kavachi is so active that further studies into the sharks have been somewhat hampered.
Just how do the sharks survive in such an active crater? Professor Heithaus believes that the sharks’
ampullae of Lorenzini (cluster of pores on their snout) enables them to detect changes in the earth’s
magnetic field before an eruption occurs.

It is thought that the ampullae of Lorenzini may also help the sharks to find other volcanic islands. “It
looked like the sharks in the volcano were used to dealing with eruptions,” Professor Heithaus said.
“You would think it’s dangerous, but studies have shown us they can detect approaching hurricanes
and cyclones, so they may be able to detect when something bad is about to happen and move out
of the way.”

(Photo from video footage taken by David Muirhead)

Although his research is still ongoing, Professor Heithaus says that the correlation between sharks
and volcanoes is undeniable. His studies have also taken him to an active volcano called Piton de la
Fournaise on the shores of Réunion Island. Swimming was banned there in 2013 because sharks are
so abundant and 11 people have lost their lives in attacks, mostly by bull sharks, since 2011.
Professor Heithaus believes the bull sharks at Piton de la Fournaise are taking advantage of the
sediment that washes down the volcano’s slopes. He says that the cloudy waters at the volcano
make an ideal hunting ground for the sharks.

(Photo from video footage taken by David Muirhead)

Sharks have been found to be “functionally extinct” on nearly one in five coral reefs. Ironically, the
extreme habitat of the volcano provides a safe-haven for them according to Professor Heithaus.
“The biggest threat to sharks by far is overfishing. There are just too many being caught and that is
being driven by the demand for fins and shark meat,” he said. “You’re not going to go fishing around
a volcano and probably some of the bigger sharks, who are predators, will be less inclined to go in
there. We may not know exactly why they are there but the fact we saw so many in a fairly short
window of time, suggests it is an importance place to those sharks. If it wasn’t a great place to live
they probably wouldn’t be there… who doesn’t like a hot tub?”

By Steve Reynolds

Steve Reynolds is the current President of MLSSA and is a long-standing member of the Society. Steve was a keen diver, underwater explorer & photographer before illness struck. He is chief author of the Society's extensive back catalogue of newsletters and journals.

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