Population Of Threatened Otters Seems To Be Leveling
By David Sneed, The Tribune, San Luis Obispo, Calif.
Jul. 1–A new federal report confirms that California’s sea otter population is growing, albeit at a slower rate in recent years.
Averaged over three years, the population grew by a tiny 0.3 percent over the past year, according to the results of the most recent annual population survey of the southern sea otter.
The iconic coastal species is listed as threatened on the endangered species list.
This year’s individual survey counted 3,026 animals, a decrease of 8.8 percent.
However, biologists use a three-year moving average to assess the status of the population because it is considered more accurate.
Such averages eliminate year-to-year anomalies. Variability, such as weather and kelp abundance, can skew the results of an individual survey.
Using the average, the population is only slightly different from last year, said Brian Hatfield, a wildlife biologist with the U. S Geological Survey at Piedras Blancas.
“Because of the inherent variability in the surveys, the lower count this spring is not alarming to me,” he said. “What does raise an eyebrow is the leveling off of the three-year average.”
The survey results reinforce a recent stock assessment conducted by the U. S. Fish and Wildlife Service.
That survey concluded that the species is recovering slowly but faces some serious threats, including high disease rates and vulnerability to oil spills.
The survey area covering 375 miles stretches from just south of Pacifica in San Mateo County south through Santa Barbara County. Surveys are conducted by spotters on land and in airplanes.
The annual surveys are useful in detecting changes in regional populations of otters and in tracking the gradual expansion of the animal’s range to the north and south.
Here are some of the highlights of this year’s study:
–Male sea otters are much more migratory than females. Males are known to make long-distance migrations between sandy-bottomed areas such as Estero Bay, Pismo Beach and Monterey Bay.
–Some of the greatest variability in otter numbers occurs in San Luis Obispo County. For example, the area from Cayucos to Hazard Canyon dropped by about 100 animals, while the area from Pismo Beach to Point Sal near Guadalupe rose by an equal number.
–In spite of sluggish growth rates, sea otters continue to expand their range. The animals are expanding faster to the south than they are from the north.
–The otter’s official range now runs from Tunitas Creek in San Mateo County to Coal Oil Point in Santa Barbara County. A handful of otters are counted outside the range each year.
–Range expansion is helping to offset stagnant otter numbers in the core of its range. The core range contains the highest densities and is where most of the reproduction takes place. The core range has remained steady over the past five years from Ano Nuevo in the north to Jalama Beach near Lompoc in the south.
Reach David Sneed at 781-7930.
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Copyright (c) 2008, The Tribune, San Luis Obispo, Calif.
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