Parrotfish strategically harvest their favourite food by rotating through algae patches, waiting for each patch to regrow before dining on it again. The fish also defend their feeding territory while the food patches recuperate sufficiently, a new study finds.
Working on Palmyra atoll, around 1,000 miles south of Hawaii, a team of researchers from the University of California Santa Barbara became aware of the fish's farming habit when they noticed many bite marks in specific areas of algae growing on dead coral.
They followed these patches through time and found parrotfish were feeding heavily in each patch for a short period of time. Then, the fish would allow that exact location to recover before returning to harvest the algae again.
In doing so, the parrotfishes are keeping coral reefs healthy. Turf algae have been shown to be harmful, even lethal, to juvenile corals. When the parrotfish bites scrape the coral, they create pockets of space without the algae, which may enable tiny coral larvae to settle and grow.
Defending their 'farms'
"The fish would come back to the same area and defend it against other individuals of the same species," said Peter Carlson, lead author of the paper published in the journal Marine Ecology Progress Series. "Essentially, they're farming by using their environment very strategically."
In areas where resources were less abundant and recovered more slowly, parrotfish movements and foraging areas were significantly larger and bites were distributed sparsely across food patches.
Because herbivores support coral reef health, many are safeguarded in marine protected areas. But to properly create and manage adequate space for these fish, managers need to know the range of their movements. A second paper took a multiscale approach to tracking parrotfish movements, which is important information for conservation purposes.