To determine which fish were most important information potentially useful for protecting them Hay and Georgia Tech graduate student Douglas Rasher moved samples of seven species of seaweed into healthy reef systems that had large populations of fish.
They set up three video cameras to watch the reef areas, then left the area to allow the fish to feed. They repeated the experiment over a period of five days in three different marine protected areas located off the Fiji Islands. In all, Rasher watched more than 45 hours of video to carefully record which species of fish ate which species of seaweed.
"The patterns were remarkably consistent among the reefs in terms of which fish were responsible for removing the seaweed," said 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."
Among the most important were two species of unicornfish, which removed numerous types of brown algae. A species of parrotfish consumed red seaweeds, while a rabbitfish ate a type of green seaweed that is particularly toxic to coral. Those four fish species were responsible for 97 percent of the bites taken from all the seaweeds.
"It's not enough to have herbivorous fish on the reef," said Hay, who holds the Harry and Linda Teasley Chair in Environmental Biology at Georgia Tech. "We need to have the right mix of herbivores."
While just four fish species consumed the large seaweeds, Rasher observed a different set of species involved in what he termed "maintenance" the removal of small algal growths before they have a chance to grow.
"Through our videos, we were able to observe both groups in action," he said. "There was not only little overlap in which fishes ate the large seaweeds, but there was also little overlap between fishes that comprised the
|Contact: John Toon|
Georgia Institute of Technology