California Sea Otter Numbers on the rise.


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Posted by . on June 21, 2004 at 13:00:26:

Observers tallied a record-high total of 2,825 California sea otters for the 2004 spring survey, led by the U.S. Geological Survey (USGS). The 2004 total marked the 2nd consecutive year the threatened population has shown an appreciable increase in numbers, up 12.8 percent over the 2003 total of 2,505 otters.

The latest 3-year running average of the 3 most recent spring counts is up 9.8 percent, to 2,490 sea otters, said survey organizer Brian Hatfield, a USGS biologist in California. The use of 3-year running averages in assessing trends is the approach recommended by the Southern Sea Otter Recovery Team to reduce the influence of any anomalous counts in a given year. For the southern sea otter to no longer be considered threatened under the Endangered Species Act, a 3-year running average count of at least 3,090 sea otters would need to be sustained for 3 consecutive years.

The recent increase in sea otters, however, apparently has not occurred across all segments of the population evenly. Most of the recent increase has been in areas dominated by male sea otters, said USGS scientist Jim Estes. Numbers of reproductive females have remained roughly stable for the past decade, or perhaps even longer.

While encouraged by the high count, the scientists have not yet fully assessed what this means for the recovery of the southern sea otter. Elevated sea otter mortality has hindered recovery of the population. We are assembling a recovery implementation team to address this and other recovery issues, said Greg Sanders, southern sea otter recovery coordinator for the U.S. Fish and Wildlife Service. Increasing sea otter numbers will help us reach our recovery goals, but ultimately we must address the underlying threats to the population.

A team of scientists from federal and state agencies, universities and the Monterey Bay Aquarium has been working collaboratively to better understand why the California sea otter has not yet fully recovered. The team is using radio transmitters and time-depth recorders in dozens of tagged sea otters to track and monitor behavior and vital signs as the animals dive and forage for food. Preliminary results from these telemetry studies are showing an increase in male survival in recent years, but not in female survival.

By very precisely and closely following these tagged individuals, we are taking a qualitatively new look into the population, said Estes. From these individuals we will be able to make a sounder assessment as to what causes them to die or acts on their mortality, and the relative proportion of various threats. Additional insight into mortality comes from detailed necropsies by the California Department of Fish and Game of freshly dead sea otters found stranded along the California coast.

The spring 2004 California sea otter survey was conducted May 6-21, from Point San Pedro in the north to Rincon Point in the south, in overall viewing conditions slightly less favorable than for spring 2003.

The spring survey is a cooperative effort of the USGS, California Department of Fish and Game's Marine Wildlife Care and Research Center, Monterey Bay Aquarium, and many experienced and dedicated volunteers. The information gathered from spring surveys is used by federal and state wildlife agencies in making decisions about the management of this small sea mammal.

On June 15, a new high-definition USGS video product was premiered on HDNet. The program, Precipice of Survival: The Southern Sea Otter tells the story of the California sea otter’s return from near extinction after the fur trade to the collaborative research effort that may provide key information for their recovery. The program will air repeatedly on HDNet over the next year. See: http://hd.net/ for broadcast information.

The USGS serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.


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