Environment & Science

California's otter population struggles; scientists probe causes

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Federal scientists say sea otters along California’s coast are dying more quickly and moving into new territory.
KPCC’s Molly Peterson reports on a new study from the U.S. Geological Survey.

The survey, state and federal fish and wildlife agents, the Monterey Bay Aquarium, and volunteers count otters every spring. They live as far south as Santa Barbara, although the population’s concentrated between Monterey and San Luis Obispo.

Sea otters thought extinct until the 1920s have rebounded pretty steadily since then. But lately that recovery has flattened out. This year, otter numbers are down nearly 4 percent. U.S. Geological Survey scientists say the otters are still reproducing as much as they used to, but mortality rates are up.

It’s a recent development, so survey officials say it’s not yet time for alarm. But federal and independent biologists are getting a handle on causes. Otters may not be eating exactly what they’d like: abalone, crab, urchins, mussels, and clams. Lab tests indicate diseases in the otters’ systems. Suspected causes include coastal runoff and human and agricultural waste.