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Fieldwork

California Sea Otters—2005 Survey Numbers Dip, But Overall Population Trend Remains Positive


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Observers tallied a total of 2,735 California sea otters during the 2005 spring survey, led by scientists at the U.S. Geological Survey (USGS). The 2005 total showed a 3.2-percent decrease in otters from the 2004 record high of 2,825. To assess overall population trends, however, little can be inferred from a single year's count. Instead, 3-year running averages are used to graph the data, as recommended by the U.S. Fish and Wildlife Service's Southern Sea Otter Recovery Plan. This approach reduces the influence of any anomalous counts in a given year.

Top graph shows number of sea otters counted in California spring surveys since 1983.  Bottom graph shows number of sea otters counted during spring surveys since 1983, plotted as 3-year running averages.
Top Graph: Graph on top shows number of sea otters counted in California spring surveys since 1983. To view additional data, see Spring Counts of Southern Sea Otter 1983-2005.

Bottom Graph: Graph on bottom shows number of sea otters counted during spring surveys since 1983, plotted as 3-year running averages. (For example, the value for 2004 is the average of the 2003, 2004, and 2005 counts.) To view additional data, see Number of sea otters counted during spring surveys, plotted as 3-year running averages.

"Despite the dip in this year's tally, the latest 3-year running average of the three most recent spring counts is up 8 percent over the previous average, to almost 2,700 sea otters," said survey organizer Brian Hatfield, a USGS biologist in California. "The meaning of the 2005 count will become clearer with additional years of averaged data points."

Greg Sanders, southern-sea-otter-recovery coordinator for the U.S. Fish and Wildlife Service, also noted that large numbers of sea otters were counted at the south end of the range during this survey. "Sea-otter range expansion into southern California is something that we will be examining closely over the next year."

The spring 2005 California sea-otter survey was conducted from May 6 to June 16, covering about 375 mi of California coast, from Half Moon Bay south to Santa Barbara. Overall viewing conditions were good to very good, comparable to conditions in 2004 and slightly less favorable than those in 2003. The spring survey is a cooperative effort of the USGS, the California Department of Fish and Game's Marine Wildlife Veterinary Care and Research Center, the 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.

A team of scientists from Federal and State agencies, universities, and the Monterey Bay Aquarium has been working collaboratively to determine causes of mortality in sea otters and the relative proportion of various threats. A USGS video about this research effort, "Precipice of Survival: The Southern Sea Otter," can be viewed online. Additional information about USGS sea-otter research is available at URL http://www.werc.usgs.gov/otters/.


Related Sound Waves Stories
New USGS Video Available Online: "Precipice of Survival: The Southern Sea Otter"
October 2004
Collapsing Populations of Marine Mammals—the North Pacific's Whaling Legacy?
October 2003
California Sea Otter Numbers Are Up for the 2003 Census
July 2003
California Sea Otter Numbers Slide for Second Straight Year
July 2002
Congressional Briefing on California Sea Otter Research
March 2002
What's Wrong with the California Sea Otter?
February 2002

Related Web Sites
Precipice of Survival: The Southern Sea Otter
U.S. Geological Survey (USGS)
Sea Otter Research at WERC
U.S. Geological Survey (USGS)

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in this issue: Fieldwork
Cover Story:
Locating Surf Scooter Nests in the Northern Boreal Forest

Further Investigation of Deep Coral Reef

Sea Otters 2005 Survey Numbers Dip

Outreach Ground Water Institute for Teachers

ISIS Group Visits USGS Woods Hole

USGS Scientists Address International Visitors

Meetings Suwannee River Basin and Estuary Integrated Science Workshop

USGS-NOAA Symposium

Publications New Fact Sheet About Landslides and Cliff Retreat

August Publications List


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