New Survey Shows Declining Numbers of California Sea Otters

Written by on July 8, 2009 in Marine Life
Sea otter in Morro Bay, California - Author: Mike Baird

Sea otter in Morro Bay, California - Author: Mike Baird

The Otter Project has published the new California sea otter count, a total of 2654 otters spotted and 3.8% down from last year’s numbers, when the survey showed 2760 animals also a decrease of 8.8% from the previous year.

The sea otter is a marine mammal native to the coasts of northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg (30 to 100 lb), making them the heaviest members of the weasel family, but among the smallest marine mammals.

The historic California otter population ranged from 12,000 to 18,000. The current population has been nursed back from a small colony of survivors of the fur hunts that nearly rendered the otter populations extinct. After recovering from an estimated stock of 10-30 animals and being considered an important success in marine conservation, the health of today’s otters is questionable.  Because of the recent declining levels as well as its particular vulnerability to oil spills the IUCN lists the sea otter as an endangered species.

“Otters are the marine version of the canary in the coal mine, and they’ve been telling us for awhile now that something’s not right,” said Allison Ford, Executive Director of the Otter Project.

To keep from drifting apart, sea otters may sleep holding hands - Author: joemess from austin

To keep from drifting apart, sea otters may sleep holding hands - Author: joemess from austin

Big oil spills – the most significant threat to sea otters as they rely on their fur to keep warm – are not the only problem to overcome.  “We’re constricting their range, putting them in contact with deadly chemicals, and booby trapping the waters,” said Ford.

Among the most serious threats to sea otters are disease and factors that contribute to immune suppression.  Otters die for all sorts of reasons, including shark bites and direct human causes such as boat strikes, and gunshot wounds.  But scientists are increasingly linking otter mortality to a combination of immune system suppression and a variety of diseases, which can lead to up to 50% of otter mortality.

The presence of legacy chemicals such as DDT in the ocean have long been considered a threat to otter health; in addition to agricultural pesticides, urban runoff deposits harmful pollutants right into the oceans.  In addition to disease, threats to otters include  fishing gear entanglement, and even violence from humans.

Otter mortality is also attributed to food limitation.  Less food can lead to disease: adult females that are most often pregnant or feeding a pup must sometimes forage fifty percent of their time.

The Otter Project believes that addressing water pollution, including agricultural and urban runoff and legacy chemicals is integral to otter health.

Sea otters at Morro Bay, California - Although it is a relatively new marine mammal lineage, the sea otter can live in the ocean at all stages of life - Author: Mike Baird

Sea otters at Morro Bay, California - Although it is a relatively new marine mammal lineage, the sea otter can live in the ocean at all stages of life - Author: Mike Baird

Copyright ©  2009 by Marine Science Today, a publication of OceanLines LLC

About the Author

About the Author: Celia is Director of Business Operations for OceanLines LLC and is a frequent contributor to both OceanLines and Marine Science Today. She is a certified diver and her favorite topic is marine biology, especially stories about whales. .

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