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Southern Sea Otter Population Decreases

Shift on Morality Rate Has Researchers Concerned for Species Recovery


Friday, July 3, 2009

For the first time since the late 1990s, the Southern Sea Otter population has declined. U.S Geological Survey (USGS) scientists say the latest three-year average (2,813 sea otters) was 0.5 percent lower than last year as population growth has apparently leveled off. Otter numbers in Santa Barbara have decreased significantly; only three sea otters were spotted between Campus Point and Coal Oil Point in the last year.

California USGS biologist Brian Hatfield hopes that, as was the case with a similar decline in the 1990s, the dip will be only a brief setback in the recovery of the population. Although the dip is not beneficial to growth, “the fact that the pup counts have continued to increase slowly is encouraging,” Hatfield said.

The more reliable three-year running averages are used to assess population trends instead of individual year totals that are affected more drastically by variations such as weather conditions, otter distribution, and other factors. Three-year averages are calculated by combining the spring census totals from 2007, 2008, and 2009.

USGS scientists and research partners are aiming their research towards pinpointing causes of mortality in sea otters, and underlying reasons for the slow recovery rate and variable population trends. The conclusions from this year’s census results are that sea otters are continuing to experience a higher mortality rate than allows for population recovery. “This highlights the need for continued efforts to understand and mitigate threats to sea otters and other species in the nearshore ecosystem,” said Dr. Tim Tinker, lead scientist for the USGS sea otter research program in California.

Although the cause of the dip in the southern sea otter population is unknown, a healthier population can more likely develop when humans are aware of the various threats facing sea otters. Harassment is a known problem, and observers have reported that some boats looking at otters move in too close and spook them. As it is to all sea animals, ocean pollution is very harmful to the otters as well as the ecosystems that they depend on, so it is crucial to monitor trash and other waste that ends up in the ocean.

Susannah Lopez is an Independent intern.

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