Predation by killer whales seen as main threat
By Summit Voice
FRISCO — Federal officials have finally completed a recovery plan for northern sea otters living along the coast of southwest Alaska, but fully recovering the species may prove to be a big challenge. The U.S. Fish and Wildlife Service says predation by killer whales may be the single biggest factor in significant population declines documented since the 1950s.
“There may be few actions that can be taken to mitigate predation as a threat, but the sea otter recovery program should search for solutions and be open to novel ideas,” the scientists wrote in the recovery plan. Above all, more research is needed to pinpoint population trends and reasons for the decline, they wrote.
The 50 to 60 percent drop in otter numbers has had a dramatic effect on coastal ecosystems in the region. Otters are a keystone species in their ecosystem niche. They control sea urchin populations, which prevents over-grazing of underwater kelp forests, which are important habitat for a slew of other species. Read the recovery plan here.
The USFWS recognizes that connection in the recovery plan:
“The recent population decline of sea otters in southwest Alaska’s Aleutian archipelago has resulted in a wholesale phase shift in the coastal ecosystem from kelp forests to deforested sea urchin barrens … In view of the sea otter’s keystone role in coastal marine ecosystems, the goal of recovery must be not only to assure the continued survival of sea otters, but also to assure that they are numerous enough to maintain kelp forests through the otter-urchin-kelp trophic cascade.”
Sea otters were nearly wiped out by the fur trade starting in the late 1800s and continuing through the early 1900s. Once the hunting stopped, populations rebounded dramatically, then started dropping again in the 1950s, suggesting more systematic ecosystem troubles in the region.
According to the recovery team, population levels in the Aleutian Islands are “perilously low, with some island groups currently having less than one-tenth the number of otters they had in 1990. This is a region where just 20 years ago the population was large and probably at or near the environmental carrying capacity.
Publication of the recovery plan, caps more than a decade of advocacy by the Center for Biological Diversity to give otters full protection under the Endangered Species Act.
“Sea otters in southwest Alaska have been in trouble for a long time and they deserve better,” said Rebecca Noblin, Alaska director with the Center. “Implementing this recovery plan will go a long way toward guaranteeing there’s a future for sea otters in southwest Alaska and, ultimately, lifting federal protections.”
Fewer than 40,000 sea otters were estimated to exist in southwestern Alaska in 2005, down from more than 100,000 in the 1970s. Declines are most pronounced in the Aleutian Islands, where the population has dropped from more than 70,000 to fewer than 10,000 animals.
The exact cause of the decline remains a mystery, but scientists have speculated that, along with increased predation by killer whales, otters in the area are also threatened by possible oil spills, along with changes to the ecosystem due to global warming and overfishing.
In August 2000 the Center petitioned the Fish and Wildlife Service to protect sea otters in southwest Alaska under the Act. Two lawsuits and five years later, in August 2005, sea otters in this region finally received federal protections, following population declines of up to 90 percent in many areas.
In December 2006 the Center filed a lawsuit in federal district court in Washington, D.C., challenging the Bush administration’s refusal to designate and protect critical habitat for sea otters, and in April 2007 the Center reached an agreement with the Fish and Wildlife Service. Under the terms of the agreement, critical habitat for the otter was finalized by October 2009.
Federal wildlife agencies are required to issue and implement a plan for the conservation and recovery of all species protected under the Endangered Species Act. Studies have shown that species with dedicated recovery plans are more likely to be recovering than species without recovery plans.
“This new recovery plan prioritizes research on the sea otters and the causes of their decline,” said Noblin. “We’ll continue to push the Fish and Wildlife Service to implement concrete actions to protect sea otters from threats ranging from oil spills to climate change to illegal hunting.”
Read more about the Center’s campaign to protect sea otters.
Filed under: biodiversity, endangered species, Environment Tagged: | Alaska, Aleutian Islands, biodiversity, Center for Biological Diversity, endangered species, northern sea otters, United States Fish and Wildlife Service