Video Study Shows Four Herbivorous Fish Eat Most of the Algae that Appears on Coral Reefs in Fiji

Two species of unicornfish as well as rabbitfish and parrotfish clean up coral reefs of seaweeds.

Written by
John Virata

Scientists with the Georgia Institute of Technology’s School of Biology have determined that just four species of herbivorous fish are the main consumers of potentially harmful seaweeds that occur on coral reefs and these fish are picky eaters. The scientists set up underwater video cameras in marine protected areas in Fiji and left the area to allow the fish to feed. In total they gathered more than 45 hours of video data on three different reefs over the course of five days. After studying the video, they determined that of the 29 herbivorous fish located on the reefs, just four fish species did most of the work (97 percent) in clearing the reefs of the seven types of seaweeds in the study. Two unicorn fish species ate a variety of brown algae, one parrotfish species consumed red algaes, and a rabbitfish consumed green alga. The scientists also noted that there was virtually no diet overlap between the groups of fish, meaning each was specialized eaters that focused primarily on a certain algae.

“We did not see much overlap in the types of seaweed that each herbivore ate,” Mark Hay, a professor in the School of Biology at the Georgia Institute of Technology said in a press release. “Therefore, if any one of these four species was removed, that would potentially allow some macroalgae to proliferate.” Hay worked alongside Georgia Tech graduate student Douglas Rasher on the study.

For more information on the Orangespined unicornfish, also known as the naso tang and naso surgeonfish, click here.

Read Douglas Rasher’s study on the effects of overfishing of herbivorous fish on Fijian reefs.

Click here to read how Fijians play a role in protecting the island nation’s marine protected areas.

They also determined that reefs in marine protected areas supported 7 to 17x greater biomass, 2 to 3x higher species diversity of herbivorous fishes and 3 to 11x more coral cover than what was found on reefs not in marine protected areas. They also conclude that certain species of fish and a certain mix of species of fish on a reef are critical to the overall health of coral reef systems.

Macroalgae, when left unchecked, can cause havoc on coral reefs. Some emit chemicals that kill corals while others can smother corals and reduce sunlight that encourages coral growth. The study was made possible in part by the National Science Foundation (NSF), the National Institutes of Health (NIH) and the Teasley Endowment to Georgia Tech.

An abstract of the report appears online in the journal Ecology. A printed version of the report will appear in a future edition.

Article Categories:
Fish · Freshwater Fish