Every three years, we visit Wake Atoll to survey corals, assess the fish populations, and collect oceanographic data for a long-term monitoring effort—the Pacific Reef Assessment and Monitoring Program. Wake Atoll has clear water, healthy coral reefs, and is managed and conserved as part of the expansive Pacific Remote Islands Marine National Monument. It has a healthy reef fish community with plentiful sharks, jacks, and groupers. As a fish research diver, it’s my kind of paradise. Sitting in the middle of the subtropical North Pacific Ocean, 1,500 miles east of Guam and about 2,300 miles southwest of Honolulu, it may be the most remote place I’ve ever been. But for me, and a few other scientists lucky enough to visit the island, there is one thing that makes Wake a special place: Bolbometopon muricatm, the bumphead parrotfish.
Parrotfish bite and scrape algae off of rocks and dead corals with their parrot-like beaks; grind the inedible calcium carbonate (reef material made mostly of coral skeletons) which is excreted as sand back onto the reef. Larger parrotfish species can take small chunks out of the reef, removing algae and the occasional piece of coral. Bumphead parrotfish are unique in that they are continuously crunching large bites out of the reef, about half of it from live coral. In fact, that’s what they do most of the day. Bite the reef. Excrete sand. Repeat. Over the course of a year a single fish can remove over 5 tons of calcium carbonate from the reef! But by selectively eating fast growing coral species over slower growing species, they help maintain a more diverse coral reef ecosystem. Also, by munching down tons of dead corals every year each fish makes room for young corals to settle, grow and build up the reef. This means breaking down “dead reef” into sand rather than it breaking off in a storm and damaging other parts of the reef. And since bumpheads often travel in groups, sometimes numbering into hundreds and traveling multiple kilometers in a day, this species can have quite an impact on the reef ecosystem. Bumphead parrotfish literally shape the reef.
In addition to having a sizable healthy coral reef around the island, Wake Atoll has an expansive, sheltered lagoon. This may be the perfect habitat for the juvenile parrotfish and allows Wake to have a healthy, self-supplying population of bumpheads. And since Wake is protected from fishing, it may be as close to a pristine home as the bumphead parrotfish are going to encounter in today’s world. Wake actually has the highest concentration of bumphead parrotfish in U.S. waters and possibly the world (although certain areas of the Great Barrier Reef in Australia also have very healthy adult populations). During my time at Wake Atoll, I had a number of chances to see them, from loose groups of just a few individuals, to a school of thirteen.
As I write this, the NOAA Ship Hi‘ialakai heads west to Guam, our next survey site where I’ll be spending eight days surveying reef fish. Bumpheads were once thought to be extinct around Guam due to overfishing, but there have been a few sightings by our scientists and partners in the past few years, of both adults and juveniles. So, while my expectations of encountering these giant bulbous-headed, coral-chomping fish are low, I sure hope I do, given how important they are to the natural function of coral reef ecosystems.
- Bellwood, D., & Choat, J. (2011). Dangerous demographics: the lack of juvenile humphead parrotfishes Bolbometopon muricatum on the Great Barrier Reef. Coral Reefs, 30(2), 549-554.
- Bellwood, D. R., Hoey, A. S., & Choat, J. H. (2003). Limited functional redundancy in high diversity systems: resilience and ecosystem function on coral reefs. Ecology Letters, 6(4), 281-285.
- Bellwood, D. R., Hoey, A. S., & Hughes, T. P. (2011). Human activity selectively impacts the ecosystem roles of parrotfishes on coral reefs. Proceedings of the Royal Society B: Biological Sciences. doi: 10.1098/rspb.2011.1906
- Donaldson, T. J., & Dulvy, N. K. (2004). Threatened fishes of the world: Bolbometopon muricatum (Valenciennes 1840)(Scaridae). Environmental Biology of Fishes, 70(4), 373-373.
- Green, A. L., & Bellwood, D. R. (2009). Monitoring functional groups of herbivorous reef fishes as indicators of coral reef resilience: a practical guide for coral reef managers in the Asia Pacific Region: IUCN.
- Kobayashi, D., Friedlander, A., Grimes, C., Nichols, R., & Zgliczynski, B. (2011). Bumphead parrotfish (Bolbometopon muricatum) status review. NOAA Technical Memorandum NMFS-PIFSC-26. NOAA.
- Muñoz, R. C., Zgliczynski, B. J., Laughlin, J. L., & Teer, B. Z. (2012). Extraordinary Aggressive Behavior from the Giant Coral Reef Fish, Bolbometopon muricatum, in a Remote Marine Reserve. PLoS One, 7(6), e38120. doi: 10.1371/journal.pone.0038120
- Munoz, R. C., Zgliczynski, B. J., Teer, B. Z., & Laughlin, J. L. (2014). Spawning aggregation behavior and reproductive ecology of the giant bumphead parrotfish, Bolbometopon muricatum, in a remote marine reserve. PeerJ, 2, e681.
- Sundberg, M., Kobayashi, D., Kahng, S., Karl, S., & Zamzow, J. (2015). The Search for Juvenile Bumphead Parrotfish (Bolbometopon muricatum) in the Lagoon at Wake Island.