LAND TEAM GOES ASHORE ON SOUTHEAST ISLAND TO MAP THE GROWTH OF AGGRESSIVE ALIEN WEEDS, PEARL AND HERMES REEF


Setting up camp on
Southeast island

Today, Hawaiian Islands Wildlife Refuge Manager David Johnson and two wildlife biologists, Chris Depkin and Eric Lund went ashore on Southeast Island at Pearl and Hermes Reef to map the growth and extent of alien weeds and other vegetation on the sandy island. Aggressive weeds like verbesina, or golden crown beard, have grown rapidly on the island over the past 5 years. The small crew will spend a total of four days on island.

Verbesina (below) is an invasive plant that grows quickly and covers over native vegetation. According to Johnson, the plant likely affects seabird breeding behavior because it grows too high and too dense for birds to nest. Seabirds like albatross tend to prefer open areas with low growing vegetation as breeding sites. Verbesina can grow several feet high and is believed to be doubling its rate of spread each year.


Introduced weed verbicina
on Southeast Island,
Pearl and Hermes Atoll

Given the small size of the islands within the atoll, the amount of land available for breeding is already limited. When an aggressive alien weed like verbesina moves in, breeding and survival become even more difficult for them," said Johnson.

When asked about why it's important to protect a little island in the middle of the Pacific Ocean, Johnson said, "This little island is serving a huge ocean. As insignificant as this sandy island may seem, in hundreds of thousands of acres of ocean, this island provides the only place for some of these seabirds to come back to, breed and care for their young.

"And we can't just protect this 34 acre island. It is one element of a larger atoll ecosystem made up of coral reefs, lagoon habitat, and pelagic waters. The animals that live here rely on the functioning of each part of the system in order to survive. When one part of the system becomes disturbed or degraded, the whole system is impacted," explained Johnson (below).


Refuge manager David
Johnson at Southeast Island

During their visit, the team will conduct vegetation surveys and develop a baseline of information on all vegetation, both native and introduced on the island. Last year a total species identification was conducted. The baseline surveys that will be conducted on this trip will build on this information and help the U.S. Fish and Wildlife Service develop a monitoring and control plan for the alien vegetation.

In order to control its spread, Verbesina typically needs to be hand pulled. Some herbicides can also be used to control the population, however wildlife officials try not to use chemicals within the refuge, to minimize impacts to other species.


Laysan Finch on Southeast
Island, Pearl and Hermes Atoll

Aside from mapping vegetation, the land team will also survey the island for Laysan finches (pictured above) that were introduced to the island to improve the chance of the species' long-term survival. On Laysan Island the bird had become seriously threatened by the destruction of habitat caused by the introduction of rabbits to that island at the turn of the century.

In 1967, 108 Laysan finches were released at Pearl and Hermes Reef. In less than 30 years, the beaks of the finches shortened, demonstrating how quickly a species can evolve and adapt to a local environment. Today there are approximately 350 Laysan finches surviving at Pearl and Hermes, the vast majority of which make their homes on Southeast Island.

Pearl and Hermes Reef is a low coral atoll located approximately 1,200 miles northwest of Honolulu. Southeast Island is the largest of seven small emergent islands in the atoll's lagoon.


Southeast island at
Pearl and Hermes Reef

The tiny island provides important breeding ground for 17 species of seabirds including the black-footed albatross. In fact, twenty percent of the world population of this large seabird nests at Pearl and Hermes atoll. Migratory birds also use the island as a resting stop in their annual travel.

On their first day on-island, the land team witnessed a half-dozen large green sea turtles (below) basking in the sand. Although no green sea turtle nesting sites have ever been recorded on island, Johnson believes that the island serves as a basking site for the threatened sea turtle. According to Johnson, Southeast Island is also a fairly significant Hawaiian monk seal pupping area in the atoll.


Turtles basking in the sun
at Pearl and Hermes Atoll

It is a common belief that the atoll was named for these pearl oysters that once were in abundance at the atoll. However, the atoll was actually named after the twin English whaling ships that ran aground there in 1822, the Pearl and the Hermes. It wasn't until 100 years later, in 1927, when the large oysters were found for the first time.

The black-lip oyster pearls were heavily fished upon their discovery, and within 3 years, 150 tons of oyster shells had already been removed and shipped to button makers in San Francisco. Concerned about the fishery and whether the population could sustain such heavy harvesting, the federal government commissioned an expedition in 1930 to search for the oyster beds. Only 480 oysters were found. By 1969, only one oyster was found.

Divers on this expedition are keeping an eye out for this pearl oyster. If any are found, it will be a significant re-discovery. It will help answer the question of whether or not a species like the pearl oyster can ever recover from over-harvesting.

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