Maps and Imagery
Click on the links below to download shapefiles which correspond to the French
Frigate Shoals detailed habitat class and aggregated cover imagery. Each zipped
shapefile consists of 6 separate files, with the same root name and .dbf, .prj,
.sbn, .sbx, .shp, and .shx extensions.
Island: Detailed habitat shapefile (7.6 MB)
Island: Habitat cover shapefile (7.4 MB)
Download a .ZIP file which contains the Arc and PCI legend files (.avl and
.rst extension) for the NWHI maps. When added to your Arc or PCI project, these
files will cause the vector colors to match the geotiffs.
Description and History
Approximately 250 km WNW of Kaua'i and 1975 km ESE of Midway lies Nihoa Island
at longitude 161 degrees 56 minutes W and latitude 23 degrees 03 minutes N.
Nihoa is estimated to be 7.2 million years old. Erosion has left only about
0.6 sq. km of what was once a large island. The sheer cliffs of the island
jut up to as high as 215 m.
Nihoa Island is the emergent portion of a large basaltic shelf that measures
about 29 km long in a NE-SW direction 16 km wide. The depth of the shelf is
typically between 34 and 66 m. In total, the shallow water shelf surrounding
Nihoa covers an estimated 487 sq. km.
Nihoa is considered to be the best example of a nearly undisturbed coastal
ecosystem in the entire Hawaiian archipelago. An estimated 500,000 birds of
17 species regularly breed on the island. The Nihoa Finch and the Nihoa Millerbird
are found nowhere else on earth.
Sheila Conant, an ornithologist at the University of Hawai'i, began studies
of the Nihoa Finch and the Laysan Finch in 1980. Her research revealed that
food type and availability has influenced the evolution of the size and shape
of the beaks of these birds. Dr. Conant's findings confirm that these birds
can adapt rapidly (produce offspring with more appropriate beaks) to changes
in food type and availability. For many years, similar research was conducted
on the Galapagos Islands by Peter and Rosemary Grant of Princeton University.
The shallow-water coral reef communities found at Nihoa are the result of
constant wave action. Throughout the year, Nihoa is constantly awash in powerful
oceanic waves. Northeasterly Trade Wind-generated waves occur throughout the
year with major impact from North Pacific swell during the winter. As a result,
sand shifting on the shelf tends to inhibit coral settlement and growth.
Nihoa has a rich cultural heritage. The island has 88 Polynesian archaeological
sites. Polynesians inhabited the island between 1000 and 1700 A.D. House sites,
sweet potato terraces and religious sites still remain from these early settlers
who had vanished from the island by the time Western ships arrived.