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Nihoa Island (23° 04' N - 161° 55' W)

Nihoa Island (23° 04' N - 161° 55' W)

Geography

The island closest to the Main Hawaiian Islands (MHI) is Nihoa.

This small basalt island lies 160 nautical miles (296 km) east southeast of Necker Island and 155 nautical miles (287 km) west northwest of Kauai and 250 nautical miles (463 km) from Honolulu.

Nihoa is the largest volcanic island in the northwestern chain, with approximately 171 acres (0.7 km²) of land. It is about a mile long and a quarter mile wide, and it is the tallest of the Northwestern Hawaiian Islands (NWHI) at 903 feet (275 m) on its easternend.

Nihoa's submergent coral reef habitat totals approximately 570 km² (140,554 acres). It was designated a wildlife refuge by President Theodore Roosevelt in 1906. Nihoa is also called "Bird Island", which translates from its ancient name, Mokumanu.

Although seemingly inhospitable, between 1000 and 1700 A.D this remote and rugged island was visited and inhabited by Hawaiians. More than 80 cultural sites have been discovered, including religious shrines, habitation terraces and bluff shelters, agricultural terraces, and burial caves. Artifacts found included fishhooks, sinkers, cowry shell lures, hammerstones, grindstones, and adzes (ax - like tools).

Terrestrial plants and animals

The terrestrial fauna include monk seals (Monachus schauinslandi), 72 species of arthropods including giant crickets and earwigs, two species of endemic land birds, the endangered Nihoa finch (Telespyza ultima) and the endangered Nihoa millerbird (Acrocephalus familiaris kingi), and several species of seabirds, such as terns, shearwaters, petrels, boobies, albatrosses, tropic birds, and frigate birds. Endemic endangered plants include the Nihoa fan palm (Pritchardia remota), the only species of tree on the island, and the leguminous 'ohai shrub (Sesbania tomentosa). Most of the ridges are covered with two species of grass and the valleys are densely covered with shrubs and bushes.

Shallow water habitats

Basalt underlies most shallow water habitats surrounding Nihoa. These basaltic habitats consist of submerged portions of sea cliffs close to shore, caves and lava tubes, ledges, overhangs, basalt pinnacles, boulders, cobbles, sand deposits, basalt benches and slopes, trenches, and shelves which are constantly punished by swells and currents. Consequently, there are few suitable habitats for strong and extensive coral colonies to grow and flourish.

Corals and algae

Coral cover is not greater than 25 percent in any habitat. Around Nihoa and the next island in the NWHI chain, Necker Island, there are only submerged reefs, no emergent ones. Most of the reefs are found at 40 ft or deeper. On the North side of Nihoa, few corals were found at depths shallower than 70 feet. Most of the corals observed are low growing encrusting species (Maragos and Gulko, 2002). Seventeen species of scleractinian (stony) coral were found at Nihoa. Small encrusting forms of the lobe coral, Porites lobata, and rose coral colonies (Pocillopora meandrina) were the most common. Encrusting pink coralline algae covered many rocky surfaces in very shallow water. Some red, brown and green algae were common around the island. The red alga, Asparagopsis taxiformis, is an edible species that is no longer common in the Main Hawaiian Islands (MHI).

Other invertebrates and fishes

The most common invertebrates found (excluding corals and other cnidarians) are the smaller encrusting species, such as sponges, ectoprocts (bryozoans), and tunicates. Large invertebrates were uncommon, except for a couple of species of rock-boring sea urchins and a starfish, the spotted linckia (Linckia multifora). Sharks, jacks, monk seals, and other apex predators (predatory animals which are at the top of their food chain and are not normally preyed upon by other predators) are common to the island. However, due to the limited number of habitat types, species diversity of reef fishes is low when compared to other atolls and islands in the NWHI. Fishes uncommon or rare in the MHI but typical of the NWHI, such as the spotted knifejaw, Oplegnathus punctatus, are often found. Nihoa supports a small population of endangered Hawaiian monk seals with limited reproduction, probably maintained by immigration from other breeding colonies.

A list of NWHI coral species (pdf,30kb) adapted from: Maragos, J., G. Aeby, D. Gulko, J. Kenyon, D. Potts, D. Siciliano, and D. VanRavensway.  2004.  The 2000-2002 Rapid Ecological Assessment of Corals in the Northwestern Hawaiian Islands, Part I:  Species and Distribution.  Pacific Science 58(2):211-230.

In order to protect the island's fragile ecosystem, few visitors are allowed on Nihoa and strict protocols are required. Approval must be given by the U.S. Fish and Wildlife Service and is mostly granted to those doing cultural and scientific research.

Link to metadata and data held by CoRIS

Click on the following URL to locate metadata and data in the CoRIS holdings on Nihoa Island. When the query screen comes up, enter Nihoa in the window, and then click on Search.
http://coris.noaa.gov/geoportal/

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