The Southern Sea Otter

By Pilar Pereyra

The Southern Sea Otter (Enhydra lutris nereis) is the smallest marine mammal belonging to the weasel family. The average male otter weighs 65 pounds and measures 4.5 feet, while females weigh 45 pounds and measure 4 feet. The otter's small stature is deceiving, however; it can eat up to 25% of its body weight each day thanks to its incredibly fast metabolism. Sea otters generally consume sea urchins, crabs, squids, octopuses and shellfish, using rocks as tools to smash open the hard shells of its meal.

http://animals.nationalgeographic.com/animals/mammals/sea-otter

Another unique attribute of the sea otter is its unusually thick fur, which provides a layer of insulation to make up for its lack of body fat and blubber. They regularly groom themselves in an effort to maintain their waterproof fur. Sea otters can often be seen clinging to kelp forests, their bodies wrapped around the kelp while they rest to keep from floating away.

This furry mammal has an average life span of 23 years. With regard to reproduction, female sea otters achieve sexual maturity at age 3, while males take as long as 5 years. As a k-selected species, female sea otters usually only give birth to 1 pup per year, although giving birth to twins is not unheard of.

Above all else however, is the Southern sea otter’s value as a keystone species; its crucial role as a predator greatly contributes to maintaining the Kelp Forest ecosystem on the Pacific coast. Without sea otters, the sea urchins and other invertebrates would decimate the available plant resources and wipe out the Kelp Forest, which is home to a wide array of endemic species.  

Geographic and Population Changes

Sea otters can be found in shallow waters along the Pacific Coast up to Alaska and coastal areas in Asia. Historically, the global sea otter population ranged from 100,000 to 1 million. However, over-exploitation due to fur trading in the early 1900’s greatly reduced the population, leaving only 1,000 to 2,000 otters left.

http://www.usgs.gov/blogs/features/files/2014/09/2014-Spring-Survey-Figure21.jpg

Protection under the Endangered Species Act

As per the criteria of the Endangered Species Act of 1973, the Southern sea otter was listed as endangered (in danger of extinction) in 1977. The ESA uses five factors to determine a species’ eligibility for protection, which are as follows:

1. Significant damage to a species’ habitat

2. Overutilization

3. Disease and predation

4. Inadequate existing mechanisms

5. Natural and manmade factors

The act also outlines that the possibility for reclassification if the Southern sea otter population falls below 500. In order for the species to be categorized as threatened, the population level over three years must be greater than 1,850 or fewer than 3,050. The only way the species can be considered delisted is if the population successfully exceeds 3,090 over a three-year period.

Cause of listing and Main threats

http://seaotters.com/resources/maps-charts-illustrations/

The Southern sea otter was initially listed in 1977 due to its small population size and sparse distribution, as well as habitat degradation due to frequent oil spills. Main threats to the species include great white shark attacks, incidental take as a result of commercial fishing, disease, pollution and oil spills.

 

Oil spills are largely the biggest threat to the survival of the species; the 1989 Exxon Valdez Oil Spill confirmed conservationists’ worst fears as oil spread over 400 miles in 30 days, causing the deaths of thousands of otters. The oil ruins insulating properties of fur, which causes the otters to die from hypothermia; if not, they succumb to the effects of oil ingestion and inhalation of petroleum fumes.

http://www.usgs.gov/blogs/features/usgs_top_story/slowly-swimming-towards-recovery-californias-sea-otter-numbers-holding-steady/

Another major threat that plagues the otters is the introduction of disease organisms and pathogens due to pollution. One case is the prevalence of “microcystin,” a toxin produced by cyanobacteria (a blue-green algae) which develops as a consequence of sewage and fertilizer runoff into lakes and rivers. Pinto Lake in California is highly prone to these algae “superblooms;” surveys in 2007 led to the discovery of dead otters found near the location of the runoff from Pinto Lake. A disease known as toxoplasma, a common parasite found in cat feces, is an example of yet another threat to the critically endangered species; these parasites are found in polluted waters that eventually infect shellfish, which are then consumed by sea otters. It is estimated that about 60-70% of male otters currently carry the parasite, which can lead to serious effects with regard to mortality and subsequent population size.

www.waterboards.ca.gov

ESA Recovery Plan:

An initial recovery plan for translocation of the Southern sea otter was proposed in 1982. The plan was intended relocate otters to the San Nicolas Island to enhance its range and population size, while simultaneously protecting it from the imminent risk of oil spills. Approved by US Congress in 1986, this newly established management zone was to be monitored by conservation agencies for the observation of population dynamics and limiting factors in a contained colony.

Studies found that the mystery of stagnant population growth was due to entanglement in fishing gear and once regulations were imposed the population began to increase steadily. However, the San Nicolas Colony was ultimately deemed a failure because of the 140 sea otters translocated, only 29 remained in 2002. Maintenance for the zone proved to be costly and ineffective, since sea otters migrated in and out of the zone seasonally.
 

http://www.seaotters.org/images/Fig-1-NoOtterZone.gif

The current plan for recovery focuses on long-term management and mitigation strategies to address the causes of the high mortality rate.

Strategies to remedy the main threats and refine previous management techniques can be broken down as follows:

• Oil Threat:

-Monitor USCG vessel management plan

-Gauge the risk of tanker accidents and other possible sources of oil spills, including off-shore oil platforms, pipelines, and marine terminals

-Develop a oil spill contingency plan that includes a sea otter response plan

• Take:

-Monitor incidental take as well as intentional take in commercial fisheries

-Evaluate the effectiveness of fishing regulations for preventing sea otter take

-Take steps to reduce or eliminate sea otter mortality incidental to fisheries.

• Disease:

-Analyze tissues from southern sea otters for environmental contaminants and archive tissues for future analysis to determine sources and levels of environmental contaminants

-Collect and analyze tissues for evidence of stress or disease, while taking steps to minimize factors causing stress or disease

-Evaluate the potential for habitat related differences in growth rates between populations of sea otters

• Previous Management Techniques:

-Estimate effective population size of the southern sea otter population (through telemetry transmitters injected into otters)

-Improve captive sea otter management techniques

http://seaotters.com/research-conservation/

What can you do?

-Support research programs such as the Monterey Bay Aquarium’s Sea Otter Program (700 otters in 30years) in part with the  U.S. Geological Survey, the California Department of Fish and Wildlife, and the University of California

-Reduce, reuse, recycle!

-Purchase environmentally friendly products, such as those labeled biodegradable

-Volunteer for beach cleanups!

-Donate to the California otter fund! (found on CA tax form 540)

http://www.usgs.gov/blogs/features/usgs_top_story/slowly-swimming-towards-recovery-californias-sea-otter-numbers-holding-steady/

Donate to support rescue programs!!

https://www.montereybayaquarium.org/support-us/ways-to-give/options/makea-general-donation

Works Cited

http://www.usgs.gov/blogs/features/usgs_top_story/slowly-swimming-towards-recovery-californias-sea-otter-numbers-holding-steady/

www.defenders.org/sea-otter/basic-facts

http://animals.nationalgeographic.com/animals/mammals/sea-otter/

http://seagrant.uaf.edu/marine-ed/mm/fieldguide/sea-otter.html

http://www.montereybayaquarium.org/conservation-and-science/our-priorities/thriving-ocean-wildlife/southern-sea-otters

http://news.nationalgeographic.com/news/2012/04/130412-diseases-health-animals-science-environment-oceans/