A Favorite Fish of Snorkelers Faces Extinction

The Chevroned Butterflyfish could face extinction due to relatively small changes in coral reefs at a time when reefs are facing unprecedented threats.

Photo: eNil / Wikimedia Commons/Wikimedia Commons

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The Chevroned Butterflyfish is the ultimate picky eater, and that's it's problem. Well, that, and human pollution.

The butterflysish (Chaetodon trifascialis) eats only a coral known as A. hyacinthus, and that coral is declining as a result of our over-saturation of ocean waters with nutrients from fertilizer runoff, sewage and other sources ("plagues" of crown-of-thorns starfish thrive in those conditions, and the starfish feast on this particular coral). Global warming, which could heat the ocean above the temperature necessary to allow this sensitive coral to survive, may also be a factor.

All of which leaves the Chevroned butterflyfish nothing to eat, according to Morgan Pratchett of the ARC Centre of Excellence for Coral Reef Studies Media Release and James Cook University, who published his research in Behavioural Ecology and Sociobiology. Even in a laboratory setting, the fish survives only in the presence of its favorite coral. It simply refuses to vary its diet, even when starvation is the only other choice.

“The irony is that these butterflyfish are widespread around the world, and you’d have thought their chances of survival were pretty good,” Pratchett said. “We call these kinds of fish obligate specialists. It means they have a very strong dietary preference for one sort of food, and when that is no longer available, they go into decline. We still don’t have a satisfactory scientific explanation for this, as it seems like rather a risky tactic in evolutionary terms – but it must confer some advantage provided enough of its preferred food is available.”

With 70% of the world's corals degraded and in decline, extinctions of specialist species like this butterflysish are likely, the scientist warned.

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