Some Fish are Picky Eaters, Causing Problems for Reefs

Written by on February 14, 2013 in Coral Reefs, Marine Life
Bleeker's parrotfish (Chlorurus bleekeri), found in Fiji.

Bleeker’s parrotfish (Chlorurus bleekeri), found in Fiji. Photo credit: Julie Bedford, NOAA PA.

Scientists have recently found that some reef fish are picky eaters which could be problematic for endangered coral reef systems.

By studying over 45 hours of footage captured from underwater cameras in reefs near the Fiji Islands, researchers discovered that only four species of herbivorous fish were responsible for removing the common and potentially harmful seaweeds that grow on reefs. In fact, these fish are so picky that each species eats a different kind of seaweed.

These findings are important because it demonstrates how certain species can be vital to maintaining a healthy ecosystem.

“Of the nearly 30 species of bigger herbivores on the reef, there were four that were doing almost all of the feeding on the seven species of seaweeds that we studied,” said Mark Hay, a professor in the School of Biology at the Georgia Institute of Technology. “We did not see much overlap in the types of seaweed that each herbivore ate. Therefore, if any one of these four species was removed, that would potentially allow some macroalgae to proliferate.”

Macroalgae, or seaweeds, can be a threat to endangered coral reefs, as some emit toxic chemicals while others smother corals. Herbivorous fish keep seaweed in check so if those fish are removed from the food chain–by overfishing, for example–the reefs will suffer.

“The patterns were remarkably consistent among the reefs in terms of which fish were responsible for removing the seaweed,” said Georgia Tech graduate student Douglas Rasher. “Because different seaweeds use different defense strategies to deter herbivores from eating them, a particular mix of fish–each adapted to a particular type of seaweed–is needed to keep seaweeds off the reef.”

Hay and Rasher found that two species of unicorn fish ate multiple types of brown algae, a species of parrotfish ate red seaweeds and a species of rabbitfish ate a particularly toxic type of green seaweed.

“It’s not enough to have herbivorous fish on the reef,” Hay said. “We need to have the right mix of herbivores.”

Reef in Fiji.

Reef in Fiji. Photo credit: Julie Bedford, NOAA PA.

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Copyright © 2013 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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