Herbivores!

by Kaylyn McCoy

Acanthuras triostegus, Convict surgeonfish forming a feeding
aggregation (photograph by Cristi Richards)

As my dive buddy and I are ascending from a dive, she points behind me and puts her hand to her forehead, making the sign for “shark.” I whip around, full of anticipation and hoping to catch a glimpse of a 12 foot Tiger Shark (Galeocerdo cuvier), preferably swimming away. But, it’s just a three foot Black-Tip Reef Shark (Carcharhinus melanopterus), cruising around below us. Big fish like sharks and jacks are exciting and important, but we can’t forget about the little guys! Above is a picture of a school of Convict surgeonfish (Acanthurus triostegus). These fish are herbivorous, and feed on the algae that grows on the reef. Certain species like these Convict Tang form dense feeding schools possibly to overwhelm smaller, but incredibly aggressive damselfish defending their territories.  Herbivorous fish play an important role in maintaining equilibrium in an ecosystem. Without these fish, certain species of algae can grow out of control, smothering the corals of the reef.

Scarus xanthopleura, Red Parrotfish
(Photograph by Paula Ayotte)

Another algae muncher that we see on the reef is the red parrotfish (Scarus xanthopleura). These fish have a specialized “beak” or dental plate used for scraping the algae off of the reef. Some parrotfish simply scrape the algae off the surface while other, usually larger species, bite of sizable chunks of the reef. Sometimes when we are counting fish, we can actually hear them feeding. Much of the sand you see on a coral reef may have passed through the belly of a parrotfish at one time or another.

Some areas of the Pacific are considering protecting specific herbivorous fish to help control invasive algae. So while it’s exciting to think about a shark snacking on a poor unsuspecting fish, don’t forget about the importance of the herbivores, the lawn mowers of the reef!