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Midway Atoll (28° 15' N - 177° 20' W)


Midway Atoll, the second most northern atoll in the world, is a circular-shaped atoll with three small islets (Sand, Eastern, and Spit) on the southern end of a lagoon. It is situated near the northwestern end of the Hawaiian Islands archipelago about 60 nautical miles (111 km) east southeast of Kure Atoll. While its land area is small, about 1532 acres (6.2 km2), the atoll has approximately 55,105 acres (223 km2) of reef area to depths of 328 feet (100 m).

Aerial view of Sand Island at Midway Atoll
Aerial view of Sand Island at Midway Atoll (Photo: J. David Rogers)
Aerial view of Eastern Island at Midway Atoll
Aerial view of Eastern Island at Midway Atoll (Photo: J. David Rogers)
Midway Atoll
Map of Midway Atoll (Map: NOAA)
Satellite image
IKONOS satellite imagery Midway Atoll (photo: NOAA)

Human activities

Midway Atoll was discovered in 1859 by N.C. Brooks, captain of the sealing ship, Gambia. By claiming Midway for the United States under the Guano Act of 1856, Midway became the only island in the entire Hawaiian archipelago that was not part of the State of Hawai'i. Midway is the most frequently visited locale in the Northwestern Hawaiian Islands (NWHI). Its geographical position as a “stepping stone across the Pacific,” made the island a critical link in cable communications (1903) and as an early trans-pacific seaplane stop (1935). Midway lies about 2,800 miles (5,186 km) west of San Francisco and 2,200 miles (4,074 km) east of Japan.

Marine biologist
A marine biologist observing a Hawaiian grouper at Midway Atoll (Photo: Keoki and Yuko Stender)

Midway served as a major U.S. military base and submarine refit base during the Second World War. The atoll's reefs were substantially degraded during the war as reef areas were dredged and filled in to enlarge land areas for airfields. Reef areas were also excavated to construct a deep harbor, navigation channels, and military fortifications and facilities. Bombing during the World War II Battle of Midway caused further destruction of the reefs and islands. The post-war era saw Midway with up to 6,000 inhabitants. Introduction of alien species, sewage discharge, chemical contamination, oil spills, and recreational fishing pressure further degraded the reef and land habitats. In 1996, the naval base was turned over to the U.S. Fish and Wildlife Service to be managed as the Midway Atoll National Wildlife Refuge. A massive U.S. Navy clean up prior to their departure removed tons of debris, leaky fuel tanks, and lead paint, as well as rats.

Today a fulltime Refuge staff of about 40 people administers a habitat restoration program, cares for the atoll's wildlife, and protects historic resources.

Terrestial vegetation

Prior to human settlement, Midway's islands consisted primarily of large sand dunes and a small variety of native plants, which included beach naupaka (Scaevola sericea), native bunch grass (Eragrostis variabilis), and beach morning glory (Ipomea pes-caprae). Over 200 plant species were introduced after human settlement, including many ornamental plants and crops. Approximately 75 percent of Midway's plant species were introductions. These include weeds, ornamental shrubs, exotic vegetables, and trees such as coconut palms and ironwood. The most common, and in most cases, invasive/noxious, introduced species include ironwood (Casuarina equisetifolia), golden crown-beard (Verbesina enceloides), wild poinsettia (Euphorbia cyanospora), haole koa (Leucaena leucocephala), sweet alyssum (Lobularia maritima), buffalo grass (Stenotaphrum secundatum), peppergrass (Lepidium virginicum), and Bermuda grass (Cynodon dactylon). Approximately 249 plant species have been reported on Midway from the time it was first discovered through 1992. Of these, 119 were known only from cultivation, 104 were intentional or accidental alien species, and 24 were indigenous. Fifteen of the native species are indigenous, or found elsewhere beyond the Hawaiian Islands, and nine are endemic to the Hawaiian Islands. None of the endemic species are restricted to Midway Atoll (Ref. 12).

The plant, Sesuvium  portulacastrum, growing amidst  coral, on Eastern Island , Midway Atoll
The plant, Sesuvium portulacastrum, growing amidst coral, on Eastern Island , Midway Atoll (Photo: Forest and Kim Starr)
Beach morning glory
Beach morning glory or pohuehue, Ipomea pes-caprae, on Midway Island. It is one of the most abundant species on rocky and sandy beaches of high islands, but is uncommon on atolls (Photo: Midway Atoll National Wildlife Refuge)


blue encrusting coral
The blue encrusting coral, Montipora turgescens, is common in the lagoon and back reef habitats of Midway Atoll (Photo: Keoki and yuko Stender)

Midway Atoll lies near the most northern limit of coral growth. Although coral diversity is less than in more tropical climates, some species (e.g., Pocillopora, Porites) are abundant. Live coral cover is low. The blue encrusting coral, Montipora turgescens is common in the lagoon and back reef habitats. Deep chasms, spur-and-groove formations, overhangs, caves, rubble and sand-filled flats, and channels in the reef create habitats for a wide variety of fishes, several of which are unique to Midway. The Hawaiian grouper (Epinephelus quernus) is reported from Midway. Large jacks (ulua) are present, but less common than in other NWHI atolls. Boarfish and knifejaws find shelter under overhangs, and large school of goatfish and bluestripe snapper have been observed. Adult and juvenile cleaner wrasses are found in the lagoon, as well as many juvenile fishes of several species. Pods of dolphins also inhabit the lagoon.

The bluestripe snapper or ta'ape (Lutjanus kasmira) forms large schools by day and forages at night. The ta’ape is an alien species intentionally introduced to the Main Hawaiian Islands from the Marquesas Islands in 1958. The species has now spread as far as Midway.

The whitesaddle goatfish, Parupeneus porphyreus, rests in small caverns and under overhangs during the day.

Map of Pearl and Hermes atoll
The whitesaddle goatfish, Parupeneus porphyreus (photo: Keoki and Yuko Stender)
The bluestripe snapper, or Ta'ape (lutjanus kasmira) (photo: Keoki and Yuko Stender)

Algae and urchins

Midway Atoll satellite image
A patch reef in Midway Atoll's lagoon (Photo: USFWS/ J. Maragos)

It is reported that Pearl and Hermes Atoll has the highest standing stock and species richness of fishes in the NWHI. These include large predators, such as sandbar sharks, Galapagos sharks, and Trevalle Jacks. In addition, angelfishes considered rare in the rest of the Hawaiian archipelago, such as the masked angelfish (Genicanthus personatus) and the Japanese angelfish (Centropyge interrupta), are commonly encounted at Pearl and Hermes Atoll.

Terrestrial plants

Click on the following links for data on terrestrial vegetation:

Midway Atoll National Wildlife Refuge ( )
Starr, F. and K. Martz. 1999. Botanical Survey of Midway Atoll 1999 Update In: 1995-1999 Baseline Surveys for Alien Species in Marine and Terrestrial Habitats on Midway Atoll National Wildlife Refuge U.S. Fish and Wildlife Service, Honolulu, Hawaii. [ Text only ] [ GPS shapefiles (.zip) ]

Martz, K. and F. Starr. 1999. Native Plant Propagation Midway Atoll National Wildlife Refuge. Report prepared for U. S. Fish and Wildlife Service, Honolulu, Hawai'i. Starr, F. and K. Martz. 1999. S. S. Midway Expedition. Trip report prepared for U. S. Fish and Wildlife Service, Honolulu, Hawai'i. [ Text only ]

Starr, F. and K. Martz. 2000. New plant records for Midway Atoll. Bishop Mus. Occas. Pap. 64:10-12.

Insects and spiders

Terrestrial insects and spiders from Midway Atoll include beetles (Coleoptera); flies (Diptera); bugs (Heteroptera); aphids and scales (Homoptera); bees; wasps; and ants (Hymenoptera); butterflies and moths (Lepidoptera); and spiders (Araneae).
Click here for a list of Midway insects and arachnids identified from Midway Atoll between 1997 and 1998. Compiled by Dr. Gordon Nishida, Bishop Museum, Honolulu, HI:


Nearly two million birds of 19 species nest on Midway Atoll. The atoll has the largest Laysan albatross or "gooney birds," colony in the world, with nearly 300,000 nesting pairs. Other birds include brown noddies, shearwaters, Bonin petrels, black-footed albatross, and the largest colonies of red-tailed tropic birds, black noddies, and white terns within the Hawaiian archipelago. One of the rarest visitors is the endangered short-tailed albatross. The bird species nesting at Midway divide the limited habitat by selecting different sites to lay their eggs, such as burrows, open surfaces, under the vegetation, and perches within shrubs or taller trees. Midway's native indigenous bird fauna also includes a small variety of arctic nesting shorebirds, such as bristle-thighed curlews and ruddy Turnstones, and a long list of vagrant species that have been observed in small numbers over the years.

Birds at Midway
A patch reef in Midway Atoll’s lagoon (Photo: USFWS/ J. Maragos)

Click here for a checklist of birds of Midway Atoll

Corals, other invertebrates, and algae

The native plant, naupaka(Scaevola sericea)
The native plant, naupaka(Scaevola sericea) (Photo: Frest and Kim Starr)

Only 16 species of stony corals have been reported from Midway from the NOWRAMP surveys. This number is probably low because of incomplete surveys of the atoll. The blue encrusting coral, Montipora turgescensis, is common in the lagoon and back reef habitats. NOWRAMP surveys reported that the back and fore reef areas hosted a moderate level of abundance of mobile invertebrate species, and low levels of encrusting species. They reported unusually large numbers of Christmas tree worms (Spirobranchus sp) on the reefs. Seagrass meadows, dredged areas, and patch reefs are common within the lagoon. Rock-boring urchins (Echinometra and Echinostrephus), calcareous green algae (Halimeda), and brown turban algae (Turbinaria) are also abundant. Common habitats on the ocean-facing reef slopes include coral spur and groove formations with overhangs and holes, and coral rubble and sand filled flats and channels. In general, live coral cover is low, although pink encrusting coralline algae are abundant.


Over 250 species of fishes inhabit the Midway Atoll lagoon and surrounding waters. Among them are hapu`upu`u, the Hawaiian grouper, usually caught at depths exceeding 148 feet (45 m) in the Main Hawaiian Islands (MHI), but often seen at diving depths at Midway. Ulua (jacks) were less common relative to other NWHI atolls. Large schools ofkumu (goatfish) and ta'ape (bluestripe snapper) were reported. Large numbers of adult and juvenile cleaner wrasses were observed in the lagoon. The lagoon seemed to support a large number of juvenile fishes. The NOWRAMP surveys reported boarfish (Evistias acutirostris) and knifejaws (Oplegnathus) under many of the overhangs. Beyond the reefs are large pelagic fishes such as sharks, tuna and marlin.

Click here for: Checklist of Reef Fishes of Midway Atoll (434 k)

The Hawaiian grouper (hapu'upu'u) at Midway Atoll.
The Hawaiian grouper (hapu'upu'u) at Midway Atoll. ( Photo: Keoki and yuko Stender)
The crosshatch triggerfish, Xanthichthys mento, is rare in very deep water except at Pearl and Hermes, Midway, and Kure Atolls . In the NWHI it is common along current-swept reefs in as little as 20 feet (Photo: Keoki and Yuko Stender)

Seals, turtles, and dolphins

Spinner dolphins swim in the Midway Atoll lagoon
Spinner dolphins swim in the Midway Atoll lagoon (Photo: Tom Ordway/ Ocean Futures Society)

The waters of Midway abound with dolphins, monk seals, and green sea turtles. Midway's beaches provide critically important habitat where monk seals raise their pups. Threatened green sea turtles are most common offshore of Sand Island's beaches, but they have been observed throughout the lagoon and surrounding nearshore waters. A population of about 300 spinner dolphins also inhabit Midway's lagoon during daylight hours. They exit the lagoon each evening to feed in deeper waters.
Click here for a list of marine life by common names: (

Click here for a list of algae, marine invertebrates and vertebrates: Other Marine Life

Click here for current research projects on Midway Atoll: (

Click here for more on: Hawaiian Green Sea Turtle
Click here for more on: Hawaiian Spinner Dolphin
Click here for more on: Hawaiian Monk Seal

Link to metadata and data held by CoRIS

Click on the following URL to locate metadata and data of Pearl and Hermes Atoll in the CoRIS holdings. When the query screen comes up, enter "Pearl and Hermes Atoll" in the window and then click on "Search"