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Relationship With Humans

The southern sea otter is an icon for coastal California, and threatened species worldwide. Sea otters are watchable, charismatic, and—in the public's eye—epitomize the purpose of the Endangered Species Act. And yet, the sea otter is one of the most beleaguered species on the planet.

In the 1700s, the otter was hunted to near extinction - estimates are that 1000 animals were left in the Aleutian Islands of Alaska and less than 20 animals found sanctuary along California's Big Sur coast. In fact, sea otters were believed to be extinct in California. A small enclave of otters was found offshore Bixby Bridge in Big Sur in 1938. All of California's sea otters are descendants of that small raft of survivors.

Sea otters were first protected by the 1911 North Pacific Fur Seal Treaty, which is considered one of the first modern International Environmental Treaties. It was too little too late for sea otters, whose numbers were so seriously depleted that they were believed to be extinct in large parts of the Pacific Rim.

In 1971 (before enactment of the Endangered Species Act), the Cannikan A-bomb test at Amchitka Island, Alaska, used a recovering population of sea otters to assess the success and power of the bomb - thousands of otters died.

In the 1970s, population growth of California's recovering population declined and otters were found to be drowning in gill nets. Legislation that limited the use of gill nets near shore resulted and the population rebounded.

California sea otters were covered by the Endangered Species Act in 1977, when they were listed as threatened. The primary reason for listing sea otters was concern over the sea otters' small population size, concentrated range, and the potential of an oil spill to wipe out the remaining sea otters in California.

Fears of what oil would do to otter populations proved founded, when in 1989, thousands of Alaskan sea otters died in the Exxon Valdez disaster. Exxon Valdez was responsible for spilling 260,000 barrels of crude oil and soiling 1,100 miles of Alaskan coastline. The spills' legacy still impacts the Prince William Sound, its residents and wildlife. A 2000 study found that sea otters were likely still being impacted by remnant oil from the 1989 spill. (Long term impacts of Exxon Valdez oil spill on sea otters; Monson et al. 2000)

After reaching a peak population of 2,400 in 1995, the California population entered a decline between 1995 and 1999. The population began increasing again in fits and starts again in 2000. As of 2009, the population has entered another decline.

The theoretical maximum population growth rate for sea otters is estimated to be between 17-20% a year (Riedman & Estes, 1990), however California sea otters have grown at an average of 4-5% a year, never surpassing a maximum of 7% a year. Populations elsewhere have grown at a rate close to the theoretical maximum. The Otter Project synthesizes agency data annually to assess current population status in a spring status report.

In addition to the fur trade, other human industries and activities threaten the existence and health of sea otter populations.

Entanglement and drowning in fisheries gear is a historic cause of sea otter population decline. Net entanglement was the cause of death attributed to 80 deaths per year in the mid 1970s. (Wendelle et al. 1985, cited in USFWS, 2003) Restrictions on gill and trammel net use addressed the severity of this problem, however certain types of fishing gear still in use remain a concern. Sea otters are known to enter crab traps, lobster pots, and other "trap" styled gear, however there is little information available on otter deaths due to entrapment. Gill nets and other harmful types of gear are also still in use in parts of the sea otters historic range, such as the no otter zone. This will become more of a concern as sea otters move south.

Fisheries interactions are also a concern in southern California, where a no otter zone artificially limits the range of sea otters in an outdated policy known as the no otter zone. Although otters are no longer removed from the no otter zone, they have limited protections in southern California. Certain fisheries are hostile to otters, and there is anecdotal evidence of California sea otters being shot, run over by boats, and harassed in the no otter zone.

A large focus of human impact on sea otters is currently the high levels of disease found in sea otter carcasses. More than 50% of analyzed sea otters die as a result of disease. The majority of infectious diseases being found in California sea otters are the result of pathogens that are not considered "natural" to sea otters. (K. Lafferty as cited in USFWS 2003)

Sea otters are also at risk from oil spills. Because otters rely on their thick fur to thermoregulate in icy Pacific waters, they are particularly susceptible to oil contamination. When oil soils their fur, water seeps through and they generally die of hypothermia. On the occasion that they are able to groom the oil out of their fur, oiled otters may still suffer from oil related chronic conditions from ingesting oil, such as lung, liver and kidney damage.

Sea otters largely stay away from people in the wild. They are protected by the Marine Mammal Protection Act, which means it is illegal to harass or harm sea otters. If you find a hurt, stranded, or dead sea otter, do not approach it. Information for how to handle sea otter emergencies can be found on our Emergency Contact page.

Visit our Current Projects to find out how The Otter Project addresses these threats to California sea otters.

The Otter Project is able to mitigate human impact on sea otters with the support of individuals like you.

Donate today to support our work to save sea otters!


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