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French Frigate Shoals

French Frigate Shoals is an open atoll consisting of a large, crescent-shaped reef surrounding numerous small, sandy islets. While the land area is only ¼ square kilometer (67 acres), the total coral reef area of the shoals is over 938 square kilometers (232,000 acres).

La Perouse Pinnacle at sunset. Photo by Aulani Wilhelm.French Frigate Shoals exhibits the classic features of a well-developed coral atoll. The coral growth is atop an eroded volcano, which has been submerged for millions of years. A steep-sided basalt pinnacle juts out of the water in the center of the atoll. This unique rock formation is the last remnant of the original volcano. The pinnacle was named "La Pérouse Pinnacle" after Compte de La Pérouse, who visited the atoll in 1786. In the moonlight the pinnacle so resembled a full-rigged sailing ship that it lured more than one vessel to her doom on the shoals as Captains investigated the unidentified companion

Tern Island, a part of the atoll, was formed into a runway to serve as a refueling stop for planes enroute to Midway during World War II. The original seawall, runway, and some of the buildings remain. Runway on Tern Island.  Photo by U.S. Fish and Wildlife Service.The U.S. Fish and Wildlife Service continues to maintain a field station there, which is staffed year-round by two permanent employees and a handful of volunteers.

The reef system associated with French Frigate Shoals supports the greatest variety of coral species in the NWHI with forty one species of stony corals documented. These include table, finger, and lobe corals. Table corals of the genus Acropora, which are common throughout reefs of the central and south Pacific, are essentially absent in the Main Hawaiian Islands (MHI) but are common at FFS. The chevron butterflyfish (Chaetodon trifascialis), which feeds exclusively on polyps of Acropora corals, is likewise absent in the MHI but common at FFS. It also supports more than 600 species of invertebrates such as sponges, coral worms, snails, lobsters, crabs, shrimps and clams, oysters, sea urchins, and sea stars. Many of which are endemic species.

More than 150 species of algae live among the reefs, including red, green and brown algae. Especially diverse and lush algal communities are found immediately adjacent to La Perouse Pinnacle, leading phycologists (algae scientists) to speculate that influx of additional nutrients in the form of guano are responsible for the high algal productivity in this habitat.The outer reef waters support gray reef sharks, butterfly fish, and large schools of jacks and groupers. Endemic masked angelfish (Genicanthus personatus) are occasionally seen here at scuba diving depths. In the Main Hawaiian Islands, they are rarely seen shallower than 300 feet.

Green sea turtle eggs.  Photo by Aulani Wilhelm.Hundreds of green sea turtles inhabit French Frigate Shoals. Over 90% of the threatened Hawaiian population of green sea turtles travel to the shoals for safe nesting. Satellite tagging of these turtles indicates that most of them migrate to the Main Hawaiian Islands to feed and reach sexual maturity before returning to French Frigate Shoals to breed. Some of these turtles travel northwest to feed, while others travel as far south as Johnston Atoll.

The many small islets of French Frigate Shoals provide refuge to the largest sub-population of endangered Hawaiian monk seals. Preserving this atoll is critical to their survival.

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Talk About It!

Where did the name "French Frigate Shoals" come from?

Asked by Student from Windward Community College on Sep 19, 2002.
Where did the name "French Frigate Shoals" come from? Did it come from frigate birds?

Answered by the NOW-RAMP Crew on Sep 20, 2002.
The name came from two French frigate ships that narrowly averted running aground on the reef in 1786. From more information, see Mark J. Rauzon's book, "Isles of Refuge."

Differences in coral proliferation

Asked by Student from Windward Community College on Sep 19, 2002.
What conditions exist differently in French Frigate Shoals that allow the table coral to proliferate as opposed to the conditions here on Oahu?

Answered by the NOW-RAMP Crew on Sep 20, 2002.
Please take a look at the Mystery of the Corals article under the Features section for your answer!

How can I volunteer at Tern Island field station?

Asked by Dan from n/a on Dec 1, 2003.
How can I volunteer to work at the Tern Island field station?

Answered by Ann Bell from USFWS on Dec 4, 2003.
The application process to volunteer can best be explained by contacting Tern Island Manager Dominique Horvath at 792-9554 or e-mailing her at

Acropora mystery

Asked by Gerard from APU on May 13, 2004.
First thank you for creating this site, you guys do a great job. My question is in regards to the Acropora mystery. I am aware from literature of two historical Acropora heads collected off the South Coast of Kauai, and it mentioned that there are currently just a handful of Acropora colonies growing in the Main Hawaiian Islands, I did not know this. I am curious as to what where exactly and how many of these colonies and what species (Valida or Cytherea) have been discovered. This subject has interested me for a number of years, and I wrote an article on it College. I would be interested in any specific information on Hawaiian Acroporiids you could send me/ direct me to. Thank you very much!

Answered by Jean Kenyon (onboard the Hi`ialakai) on Oct 13, 2004.
With the exception of a couple of Acropora colonies recorded from Kauai, the coral genus Acropora has only been recorded in the NWHI, between Necker and Laysan. Seven species have been recorded to date. The genus is most diverse and abundant at French Frigate Shoals, and secondly at Maro Reef. More information can be found in the following scientific publications:

Maragos et al (2004) 2000-2002 Rapid Ecological Assessment of Corals (Anthozoa) on Shallow Reefs of the Northwestern Hawaiian Islands. Part 1: Species and Distribution. Pacific Science 58 (2): 211-230

Kenyon, JC (1992) Sexual reproduction in Hawaiian Acropora. Coral Reefs 11: 37-43

Grigg, RW, J Wells, and C Wallace (1981) Acropora in Hawaii. Part 1. History of the scientific record, systematics and ecology. Pacific Science 35: 1-13.

Animals that are endemic to Kanemiloha'i

Asked by Ashley from school on May 19, 2004.
What tye of animals are endemic to Kanemiloha i?

Answered by Andy from NOAA on May 19, 2004.
About 25 percent of all marine organisms in the NWHI are endemic to the NWHI. As for animals that are only endemic to Kanemiloha`i I do not have any information on this.

Tern Island Runway

Asked by Kaidden from Kamehameha Schools-student on May 19, 2004.
What happened to the runway on Tern Island?

Answered by Andy from NOAA on May 19, 2004.
The runway is still there and still in use. This year, in 2004, the seawall that protects the runway from erosion is being re-constructed. The runway allows small supply planes to come and go and support the research station located there.

The runway was originally constructed in 1942, and dramatically increased the size of the island.

For more information on Tern Island see:

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Index map showing the location of French Frigate Shoals.

Bathymetric map of French Frigate Shoals. Click for large map.

IKONOS image of French Frigate Shoals. Click for larger image.

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