Biologists track sea otter decline.
For the U.S. Fish and Wildlife Service's Alaska Marine Mammals Management Office in Anchorage, monitoring sea otters (Enhydra lutris) and other marine mammals around the Near Islands and other Aleutian Islands might not be possible without support from the Alaska Maritime Refuge's research vessel, the M/V Tiglax (pronounced (TEKH-lah--the Unangan or Aleut word for eagle).
"The Tiglax is really the lifeline out there. If you want to get to the islands in the Aleutian chain, there's no other way to get all the way out there," says Douglas Burn, supervisory wildlife biologist for the Marine Mammals Management Office. The Service's wildlife biologists use the Tiglax as a base from which to survey and examine live sea otters around the Near Islands and another island group in the central Aleutians. After counting sea otters for eight to 12 hours in a small skiff, the biologists return to the Tiglax every evening to dine, sleep, and prepare for the next day of surveys.
The Tiglax, commissioned in 1987, spends May through October voyaging the waters along the vast Alaska Maritime Refuge, which is composed of more than 2,500 islands, spires, rocks, and coastal headlands spanning thousands of miles and four time zones. The vessel typically covers about 10,000 miles (16,090 km) each year. This year, the
Tiglax will support field camps for bird research on seven remote locations, invasive species removal on some islands, and other research by international teams of biologists, entomologists, volcanologists, geologists, and archeologists from a variety of government agencies and universities.
"The Tiglax supports the refuge's objective of managing trust resources and serving as a forum for international research," says wildlife biologist Jeff Williams, who is responsible for reviewing research proposals and scheduling space on the 22-passenger vessel. The Marine Mammals Management Office's research is a natural fit since sea otters are one of the refuge's threatened species, he notes.
Sea otters, the world's smallest marine mammals, live in shallow coastal waters, mostly feeding on bottom-dwelling invertebrates such as crabs, octopi, and urchins. They spend most of their lives in the water, where they mate, bear their young, feed, and socialize. They are known to wrap themselves in kelp as an anchor while resting. Sea otters float together in groups of anywhere from a few to 100.
There are three recognized subspecies. The Russian northern sea otter (Enhyrda lutris lutris) ranges from the Kuril Islands to the Commander Islands in the western Pacific Ocean. The southern sea otter (Enhydra lutris nereis) is found off the coast of Central California. The largest group--and the focus of the widest conservation efforts--is the northern sea otter (Enhydra lutris kenyoni), native to Alaska and the Pacific west coast from the Aleutian islands to northern Oregon. The estimated 73,000 members of this group now make up 90 percent of the world's sea otters.
Behind that statistic is a bloody history. The head count represents a comeback from the early 1900s, after fur hunters had driven all three subspecies almost to extinction. The world sea otter population, once estimated at 300,000, fell below 2,000, scattered in tiny remnant groups. Survivors inhabited only a fraction of their historical range.
With the end of commercial hunting, sea otters began to recover, recolonizing some of their former territory. But land development and pollution, particularly in the form of oil spills, have exacted a toll. The 1989 Exxon Valdez spill of 11 tons of crude oil into Prince William Sound, for example, killed more than 3,900 sea otters.
In recent years, the population of northern sea otters has once again shown a steep pattern of decline. In 2005, these sea otters were listed federally as threatened under the Endangered Species Act. They join the southern sea otter, which was already listed as a threatened species.
In 1992, Service biologists conducted the first population survey of northern sea otters in Alaska in 27 years. This air survey showed that the animals had recolonized all of the Aleutian Islands, but in the core areas where they had been abundant in 1965, their numbers had dropped by about half. The worrisome declines continued in surveys through 2004.
At first, scientists viewed the Service findings with skepticism. "To many people, it seemed that there was no way sea otters in such a remote, pristine environment could have suffered such a population decline," said Burn. But skepticism gave way to alarm as surveys by other scientists confirmed the Service findings.
It is not clear why the sea otter population in southwestern Alaska is plummeting. Their food supply appears ample, and scientists who have examined the animals have found no signs of unusual disease. One hypothesis by James Estes, a marine ecologist at the University of California at Santa Cruz, is that killer whales are preying more on sea otters because their traditional quarry of Steller sea lions and harbor seals is scarcer.
A Cooperative Effort
To track disease and toxins and perhaps solve the mystery, Marine Mammals Management biologists have examined the carcasses of more than 100 sea otters each year since 2002. The specimens help the scientists establish a health baseline that may prove useful if the species' decline spreads beyond southwestern Alaska. Alaska Maritime Refuge staff and an intern collect more than 60 of the carcasses from the beaches of Kachemak Bay in south-central Alaska.
Alaska Maritime Refuge wildlife biologist Leslie Slater and biological technician Arthur Kettle have spent many hours collecting and shipping otter carcasses to Marine Mammals Management. They race the clock and tides, even on weekends, because fresh carcasses have the most research value. "They are really unsung heroes," say Marine Mammals Management office biologist Verena Gill, who manages the study of sea otter disease.
Together, the efforts aim at gaining a better understanding of the threats to recovery for sea otters in southwestern Alaska. The Service has convened a team of experts to help develop a recovery plan by late 2009. "Alaska Maritime Refuge and the Tiglax will have a key role in implementing that recovery plan," Burn predicts.
Kendell Slee is a free-lance writer with long experience in conservation reporting.
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|Title Annotation:||Alaska Maritime National Wildlife Refuge|
|Publication:||Endangered Species Bulletin|
|Date:||Sep 22, 2009|
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