sign in sign up
<<
Home , Sea otter conservation

The Near- of the Southern Sea Otters, (Enhydra lutris nereis), along ’s Coast

Abby Estebat ENVS 190 Thesis December 28, 2018

Table of Contents

Abstract ...... 3 Introduction ...... 4 Background ...... 5 Near-Extinction of the Southern ...... 5 Policies & Regulations Protecting Sea Otters ...... 6 Range & ...... 7 Biology ...... 8 Stressors ...... 9 Conservation Efforts...... 10 Monterey Bay ...... 10 Aquarium of the Pacific ...... 11 Friends of the Sea Otter ...... 11 The Otter Project ...... 12 Thesis ...... 12 Method ...... 12 Findings ...... 13 Predation ...... 13 Water pollution...... 13 Disease ...... 14 Conclusion ...... 15 Recommendations...... 17 Captive Breeding ...... 17 Acknowledgements ...... 18 References ...... 19 Appendix ...... 24

Page | 2

Abstract

The Southern sea otters in the Pacific Ocean along California’s coast was thought to be extinct due to the fur trade, and a number of stressors and threats. A small population of

50 sea otters were eventually discovered near . The purpose of this thesis is to learn about how current serious threats are affecting the Southern sea otter population that remains today, and to suggest that captive breeding could be an effective method to protect and help the Southern sea otters to recovery. The literature review conducted indicates that the endangered sea otters are vulnerable to bites, microcystins produced by harmful algal blooms, and protozoal encephalitis. These threats are causing their mortality. Captive breeding has been analyzed as a method that will bring the sea otters together in one concentrated area for monitoring. The population can be protected from predators. The ocean can be regularly tested for marine pollution. The sea otters can be checked for diseases and be treated. The goal of captive breeding would be to protect the Southern sea otters from these threats and help them recover and grow into bigger populations.

Page | 3

Introduction

In the past, the fur trade of the 18thand 19thcentury played a major role in bringing

sea otter (Enhydra lutris nereis) populations to near-extinction around the world (Larson et

al. 2012). In the Pacific Ocean along California’s coast lives the Southern sea otter, also

known as the California sea otter. This particular population was thought to be extinct

until 50 of them were discovered in Big Sur in 1938 (Jessup et al. 2007). Sea otters are a

because they play an important role in the marine ecosystem, specifically

in communities, and they affect other species (McKie 2016).

As a keystone species, sea otters strongly influence the abundance and diversity of

species, such as fin and kelp-dependent organisms, within its kelp ecosystem (Jessup et al. 2004). This role consists preying on sea urchins that eat kelp and could create barren stretches of coastal habitat (Cannon 2012). Kelp forests are not only important to the local species that depend on it for habitat and protection, but to global environmental health in terms of carbon dioxide (McKie 2016).

Kelp’s high biomass has the ability to sequester carbon dioxide from the atmosphere

(McKie 2016), converting it into sugar fuel using sunlight and water, and releasing it back into the air as oxygen (Cannon 2012). Without the abundance of kelp (Figure 1), the

increasing carbon dioxide from human activities will have less potential to be absorbed

from the atmosphere. Sea otters promote healthy growing kelp forests by keeping sea

urchins in check.

Several programs have been implemented to help the sea otters recover. They were

listed under the United States Act in 1977 (Southern Sea Otter) and is fully protected under California state law (Doroff & Burdin 2015). Presently, the

Page | 4 population has stabilized to approximately 3,000 sea otters (Jessup et al. 2007), but are still struggling, as they have been experiencing other stressors and face many new threats.

The purpose of this thesis is to learn about how current serious threats are affecting the Southern sea otters living along California’s Coast. These threats include their vulnerability to predation, marine pollution, and diseases. This thesis will also provide understanding of how to help mitigate sea otter population decline and mortality by further examination into the possible solution of captive breeding. Captive breeding may be an effective method necessary to protect sea otters more effectively, so they can continue to recover.

Background

Near-Extinction of the Southern Sea Otter

Before the 1900s, thousands of sea otters used to occupy the oceans all around the globe. At one time, there were about 16,000 of them along the entire coast of California

(Jessup et al. 2007). Their drastic population decline began in 1741 when the economic value of sea otter pelts was discovered by Russian explorers (Cannon 2013).

In the very early days of the United States, Spain eventually expanded their empire to California, and was able to reach and the American Southwest for control

(Carlson 2002). The entire Northwest of the Americas would be untouched by Spain initially. In 1733, Spain began to explore this area and was introduced to the sea otter. At this point, the profitable sea otter fur trade would emerge along with many other competitions who wanted their share of the wealth.

Page | 5

Spain gathered sea otter fur that they traded with China, but Spain had very limited supply to offer China (Carlson 2002). Along with Spain, Russians had their own hand in the fur trade market with sable fur, and were soon trading sea otter fur with China. However, before the Spanish and Russians, the Chinese were receiving sea otter fur through their relationship with natives from the and Kamchatka. As Spain was exploring the South Americas during the 18th Century, reached Kamchatka and would make them late in arriving to . Expanding naturally towards Kamchatka gave

Russians access to an area that was rich in furs. Russia had an exceeding amount of interest in the North Pacific since ships were returning with cargos of fur from their expeditions. Through Russian discovery, fur trade became important to their whole economy.

In China, sea otter pelts were considered a prized possession, so Russians sold furs to their market (Doroff & Burdin 2015). China’s demand for fur lead to Russia to be one of the to engage in the fur trade. The Russians were responsible for enslaving natives to do the hunting for them. Hunting the animals and dressing the furs required techniques and skills (Etkind, 2011). The Russians also kidnapped native women and children and held them captive to possess fur through exchange with the men. Eventually, the sea otters were eliminated towards extinction. During the time span of only 30 years, their populations dwindled from 16,000 to 50 sea otters.

Policies & Regulations Protecting Sea Otters

Due to the near-extinction of the Southern sea otters, the International Fur Seal

Treaty was signed in 1911 to ban hunting which saved the remaining few sea otter populations (Cannon 2013). The Protection Act of 1972 also protects the

Page | 6

Southern sea otters of California (U.S. Department of Interior). This act protects all marine mammals that are in United States waters. Still today, the sea otters are exposed to many threats and stressors that need to be studied to bring them back to healthy populations.

In addition, the sea others were listed as endangered under the United States

Endangered Species Act in 1977, while under the California Endangered Species Act they are fully protected (Southern Sea Otter). The reasons for being listed were mainly due to reduced range and population size, and vulnerability to oil spills.

At present, the International Union for the Conservation of Nature Red List of

Threatened Species has the sea otters listed as endangered due to large-scale population declines (Doroff & Burdin 2015). The end of the fur trade and the signed treaty helped prevent the extinction of the sea otters and slowly recovered to about 3,000. However, sea otters are also experiencing new issues that are causing mortality and decline.

Range & Habitat

Sea otters historically ranged throughout the north Pacific, Hokkaido, Japan, through

Aleutian Islands, the Alaskan Peninsula, and south along the Pacific Coast to Baja California,

Mexico (Doroff & Burdin 2015). In particular, the Southern sea otters extended entirely along California. Today, they are mostly found near the central coast of the state from

Santa Cruz to Santa Barbara (Figure 2).

Sea otters live near shore marine environments and rocky sea bottoms in thick kelp forests. Kelp forests are utilized as a place of rest, protection from predators, and foraging

(Sea Otter Habitat). The strands of kelp provide protection from the rough water and currents while the sea otters are sleeping (Kenyon 1969) (Figure 3). Sea otters live closer to the surface at about less than 300 feet deep, but can dive deeper to forage for food. They

Page | 7

spend most the time floating on their backs at the ocean’s surface and are usually found in

groups (Sea Otter), especially in in the open sea (Kenyon 1969).

Biology

Sea otters are the smallest marine mammal in North America (U.S. Fish and Wildlife

Service). At birth, sea otter pups weigh about 3 to 5 pounds and reach up to 45 pounds for females and 65 pounds for males. Male sea otters grow up to 4.5 feet while females grow

up to 4 feet. The male life cycle at 10 to 15 years is shorter than the female life cycle at 15

to 20 years. Sea otter sexual maturity occurs around 5 or 6 years for males, whereas females reach sexual maturity earlier around 4 or 5 years. Female sea otters give birth to one pup at a time each year.

Sea otter pups are dependent and stay with their mother for six months until they are able to forage and venture on their own (Thometz et al. 2014). Mothers clasp her young to the chest and roll on their backs to carry her pup between her forepaws (Kenyon

1969) (Figure 4). Although pups are able to eat solid foods that their mothers provide for them, it was found that they also nurse for milk during its earlier weeks.

The sea otters’ forepaws also have claws that they use for feeding (U.S. Fish and

Wildlife Service). As adults, they dive in the waters to catch their food and use stones as a tool by pounding mussels to break them open (Hall and Schaller 1964). Their diet consists of marine invertebrates, including sea urchins, and rock (Kannan et al.

1998). In particular, feeding on sea urchins help control population and prevents them from overconsuming and decimating the kelp forests that sea otters and the community of organisms are dependent on.

Page | 8

Sea otters spend most of their life in the ocean, but are considered marine mammals

without the thick layer of blubber that seals and possess to keep them warm (U.S.

Fish and Wildlife Service). Instead, sea otters are protected by their fur which contains

about one million hairs per square inch to keep them insulated in the cold waters. The

color of their fur differs from dark brown to reddish brown. Grooming their fur is also a

part of their daily activities (Kenyon 1969).

Stressors

Since the end of the fur trade, sea otters have been affected by many other stressors

and threats. Oil spills have become one of the biggest threats to sea otters (Southern Sea

Otters [Monterey Bay Aquarium]). When an occurs in area near sea otters, oil can

ruin their fur which they need for insulation. Without their fur, sea otters are not able to

survive and they end up freezing to death. Ingesting oil or inhaling petroleum fumes also

can cause their mortality.

On March 24, 1989, an Exxon Valdez oil tanker spilled 11 million gallons on Bligh

Reef near the coast of , (Monson 2000). Thousands of sea

otters inhabited that same area and were profoundly affected by the event. Oil exposure

caused damages in sea otter organs, such as their , liver, and kidneys. Even after the

oil spill, the local sea otter population experienced continuing impacts. Although there

have not been any oil spills in California, the played a part in listing

the Southern sea otters. If an oil spill were to happen where the Southern sea otters mostly

come together, they can be defeated.

Fish and shellfish traps are also another problem. Traps are unintentionally

catching sea otters, also known as bycatch, and are causing them to drown (Hatfield et al.

Page | 9

2011). The sea otters become entrapped or entangled in various types of fishing gear, such

as nets. Hatfield et al. (2011) reveals that during a period of three years, at least 35 sea

otters drowned from tangle nets near a California fishery. Studies and experiments were

conducted and showed that sea otters are physically capable of entering the opening of

traps for Dungeness lobster, but may not be able to easily exit even with a larger

opening. Bycatch in traps are contributing to the cause of sea otters. The number of dead

sea otters could be more out there.

Conservation Efforts

Monterey Bay Aquarium

At the Monterey Bay Aquarium near the central coast of California, the Southern sea

otters are on their priority list. Their Sea Otter Program has been studying the Southern

sea otters since 1984 and promotes the conservation and recovery of their populations

with goals to rescue, treat, and release injured sea otters; raise and release stranded sea

otter pups; and find home for sea otters that cannot be released back in the wild (Southern

Sea Otters [Monterey Bay Aquarium]). The most recused sea otters are pups.

The female sea otter exhibitors are used to act as surrogate mothers and naturally

care for stranded pups that are found and rescued (Southern Sea Otters [Monterey Bay

Aquarium]) (Figure 5). When the sea otter pups have grown and are doing better, they are released back into the wild, but are continually monitored to make sure they are able to survive out on their own. In the wild it is not unusual for young otters that stray from their

mothers to associate with another adult (Kenyon 1969).

Page | 10

However, the reason for abandoned pups in the first place could be due to sea otter mothers risking their lives to raise them. The death of adult female otters usually occurs before or after weaning their pups (Thometz et al. 2014). Reproduction takes a toll on their bodies. Their bodies become deficient in nutrition and can become vulnerable to infection and disease. Sea otters naturally face energetic challenges as they have to consume 20-25% of their body mass each day.

Aquarium of the Pacific

Like the Monterey Bay Aquarium, the Aquarium of the Pacific in Long Beach which is located in Southern California also rescues stranded sea otters and finds them homes if they are not releasable back into the wild (Southern Sea Otters [Aquarium of the Pacific]).

Furthermore, the aquarium works with the United States Fish and Wildlife Service and participates in conservation programs. They loan or exchange sea otters for research with other facilities and also provide trained staff. The Aquarium of the Pacific recognizes that public health is crucial to ensure the survival of sea otters.

A wildlife biologist and adjust professor from the University of California discussed the threats to the sea otter of California (Sea Otter Conservation). If people do their part in making sure that motor oil and oil-based products, household chemicals and pet waste, are disposed of properly, they could really play a part in preventing harm and sea otter mortality.

Friends of the Sea Otter

The Friends of the Sea Otter is another organization located in Monterey who also focuses on the conservation and protection of the Southern sea otters (California

Page | 11

Programs). Amongst oil spills, they have identified that diseases and shark attacks seem to

be the highest concerns. Their organization efforts include protecting the sea otters from

fisheries, promoting the California Sea Otter Fund tax check-off, facilitating the annual Sea

Otter Awareness Week, and advocating policy changes to help the sea otter populations’ recovery.

The Otter Project

The mission of the Otter Project is to protect the watersheds and coastal oceans for

the benefit of the Southern sea otters through science-based policy and advocacy (Mission).

They have a water quality program that is allied with the Waterkeeper Alliance, a nonprofit

worldwide organization, that focuses on protecting and restoring clean water (Programs).

Thesis

Why are the Southern sea otter populations along California’s Pacific coast not

growing anymore and what is an effective method to help them recover?

Method

The method conducted for this thesis was a literature review to compile the results

of various studies on the endangered Southern sea otters including major threats that are

preventing their continuous recovery and to come up with an effective method to help

them recuperate. The literature review included scientific journals, government

documents, and other materials.

Page | 12

Findings

Predation

Shark bites are a new threat to the Southern sea otters that may be preventing their

recovery. A study revealed white shark bites on 1,870 sea otters that were found dead

(Tinker et al. 2015). White do not normally prey on sea otters for food, but they are

attacking sea otters more frequently than before. The study further suggests that there is

evidence of white sharks spending more time closer to the coastal shores. Female sharks

and their young are found in the nearshore areas of Southern California and Baja California.

Sharks are also emerging in new areas, such as northern Monterey Bay, Estero Bay, and

Pismo Beach. These areas are open water where kelp canopies are less dense

making it easier for sharks to spot sea otters underwater.

A more recent and separate study, by Monterey Bay Aquarium researchers, reveals that nearshore habitats with declining kelp cover canopies are constraining the sea otter population by limiting dispersal of reproductive female otters (Nicholson et al. 2018).

Because females are highly dependent on kelp canopy for nursing and rearing pups, the incidence of gaps in kelp canopies is life threatening. Gaps between sea otter habitat have been associated with high rates of shark bites as well as neurological disease.

Water pollution

Recent studies show that Southern sea otters are becoming more vulnerable to

anthropogenic factors. On top of oil spills and fish traps, water pollution and diseases that

impact the sea otters are also related to human activities. Sea otter deaths are being linked

to toxin from freshwater bacteria that are going out into the ocean (Stephens 2018). Miller

et al. (2010) explains that microcystins from freshwater habitats caused 21 sea otter

Page | 13 deaths through biomagnification. Biomagnification is the process in which the concentration of a substance or toxin increases as it is consumed by organisms at higher levels in a food chain (Biomagnification). The top consumer is the most affected, in this case the sea otter. The study found that sea otters were eating which were exposed to microcystins (Miller et al. 2010).

Microcystins are produced by harmful algal blooms which form in rivers and streams due to nutrient pollution (Miller et al. 2010). According to the Environmental

Protection Agency, nutrient pollution comes from human activities such as agriculture, storm water, wastewater, fossil fuels, and chemicals used in homes (Sources and

Solutions). Agriculture is the largest polluter coming from animal manure and excess fertilizers used for crops and fields. Consumers also use fertilizers for their yards. In addition, pet waste, soaps and detergents contribute pollution. When it rains, the pollutants are washed away into waterways that ultimately lead to the ocean.

Because sea otters live so close to the coast of California, they are very susceptible to agricultural pollution. Agriculture is a big part of California. As of 2016, California exported over 20 billion dollars of agricultural commodities including almonds, wine, and dairy (California Agricultural Production Statistics). As long as California is able to continue benefiting from agriculture and providing for the rest of the country, fertilizers used for land will also continue to be in use and potentially affect California’s sea otters and their marine environment.

Disease

Sea otters have also been very sensitive to chemical contamination that causes diseases and is defeating sea otter health and recovery. In the past, concentrations of

Page | 14 butylin compounds were found in sea otter tissues (Kannan et al. 1998). Tributylin was used a lot for marine paint to stop barnacles and slime from sticking against boats.

However, the removal of tributylin into the marine environment affected other organisms as well, including the sea otters. Eventually, the use of tributylin was regulated and decreased but the aftereffects continued on. Kannan et al. (1998) explained that greater levels of butylin compounds were found in the invertebrates that sea otters feed on. Due to the high food intake of sea otters and biomagnification, sea otters accumulated even higher concentrations of butylin compounds which resulted in deaths.

An additional study found that diseases caused by parasites, bacteria, or fungi, and other diseases without a specific cause resulted in 63.8% of sea otter deaths (Kreuder et al.

2003). Specific diseases, such as and Sarcocystis neurona, caused encephalitis which is associated with cardiac disease and mortality. Toxoplasma gondii and

Sarcocystis neurona are parasites that are found in cats and opossums, respectively, which are land-based pathogens leaking into coastal waters. Kreuder et al. (2003) discusses that the increase of domestic cats and opossum populations as well as the lack of watershed runoff filtration are exposing the sea otters to pathogens.

Conclusion

Sea otters are an important keystone species in marine ecosystems, especially the kelp communities (Jessup et al. 2004). Thousands of species live in and use the kelp forests for protection. Without the sea others, the marine ecosystem can be decimated by sea urchins. Because sea otters are vulnerable to many threats, especially predation, water

Page | 15

pollution, and diseases, it is vital to understand how to protect them and come up with

solutions or programs and to the helpless Southern sea otters.

In several studies that were reviewed in this paper, the Southern sea otters of

California’s coast had increased from the time less than a hundred were found remaining.

Several policies to prevent them from being hunted to extinction had to be implemented.

Organizations and programs have also helped save them when stranded and studies have been done to help learn more and increase awareness about them. However, problems continue to arise and the sea otters have been increased their numbers higher.

Human activities, the changing environment, and other factors have halted the sea otters’ comeback to about 3,000. A rising number of deaths are being caused by more frequent predation and many different types of diseases. According to the Sea Otter

Recovery Plan by the United States Fish and Wildlife, in order for the southern sea population to be reclassified from endangered to delisted under the Endangered Species

Act, their average population level over a 3-year period needs to exceed 3,090 sea others.

As of 2018, the sea otter population has reached its third consecutive year of maintaining the average to become delisted (Central Coast Sea Otter Population Remains

Stable). However, Lilian Carswell, the Southern Sea Otter Recovery &

Coordinator of the United States Fish and Wildlife states that factors influencing the population will still need to be reviewed before making the decision to delist the endangered sea others.

Objectives of the recovery plan are to “create conditions that will allow the Southern sea others to increase in numbers and distribution and to identify appropriate conservation actions to address the threats to this species” (United States Fish and

Page | 16

Wildlife). To increase population and distribution, a translocation program was conducted

by moving the sea otters to San Nicolas Island. After translocating 140 sea otters, they

found that the plan was not very successful and the goals were not being met. Therefore,

they concluded that the Southern sea otters would expand faster in California instead of

moving them to another place.

Recommendations

Captive Breeding

A possible alternative solution to protect and conserve the sea otters that would

eventually allow them to expand their distribution range is captive breeding. Although

captive breeding intends to reintroduce a species back into the wild, the program is

considered controversial. According to Sharifi and Vaissi (2014), there are disadvantages associated with captive breeding such as quick adaptation to the captive environment and risks in the wild regarding breeding and natural selection. It requires protocols for management and acclimation to new environments, health screening, and after release

monitoring.

On the positive side, captive breeding and reintroductions have also become an

important tool in the conservation of endangered or (Sharifi and Vaissi

2014). Since the Southern sea otters have already been extensively studied and there are

several organizations that been successful in rescuing and releasing them, such as the

Monterey Bay Aquarium and the Aquarium of the Pacific programs, captive breeding could

be the next best step for the recovery of the sea otters. Since translocation proved to be

unsuccessful, a new concept needs to be attempted.

Page | 17

The recommendation would be to construct a captive breeding facility modeled after the to house and care for the sea otters that will be taken captive temporarily. The facility should be located between the coasts of Monterey Bay and Long

Beach. The intent of the program would be to be able to monitor and protect the sea otters by preventing sharks from having access to them, to continuously test water quality in the area, and also be able to treat sea otters who are sick with diseases. The aquarium would have to big enough to separate healthy sea otters from the sick ones.

Before being reintroduced back into the wild, captive sea otters should be trained to learned habits that they will need to survive in the wild. Teaching sea otters to defend themselves or hide from predators may be challenging. Catching diseases will be inescapable in the wild, but bringing awareness to and creating environmental policies for those who live near waterways and the coasts have the potential to improve or prevent less exposure of pollution and diseases to the Southern sea otters.

Acknowledgements

This work was made possible by the fascinating Southern sea otters that are requiring the help of human intervention to help keep them surviving and then thriving on the coastal waters of California. Thanks to the conservation organizations and programs that are saving the sea otter pups and populations, and to the contributors of the Environmental

Studies Program at Sacramento State University, California. I appreciate Dr. Stevens and the other professors that been a part of my educational experience; my classmates that have been there for moral support; and for Justin Dela Cruz, the rest of my family, and friends who have been literally by my side and cheering me on from the sidelines.

Page | 18

References

Biomagnification. (n.d.). Retrieved December 28, 2018, from https://www.thefreedictionary.com/biomagnification

California Agricultural Production Statistics. (n.d.). Retrieved December 26, 2018, from https://www.cdfa.ca.gov/statistics/

California Programs. (2015, January 23). Retrieved December 28, 2018, from http://www.seaotters.org/california-programs/

Cannon, J. C. (2012, September 7). Thanks to Sea Otters, Kelp Forests Absorb Vast Amounts of CO2. Retrieved December 28, 2018, from https://seaotters.com/2012/09/thanks-to-sea-otters-kelp-forests-absorb-vast- amounts-of-co2/

Cannon, J. C. (2013, December 26). The Legacy of the Fur Trade. Retrieved December 12, 2018, from https://seaotters.com/2012/03/the-legacy-of-the-fur-trade/

Carlson, J. D. (2002). The Otter-Man Empires: The Pacific Fur Trade, Incorporation and the Zone of Ignorance. Journal of World-Systems Research, 8(3), 390-442. doi:10.5195/jwsr.2002.261

Central Coast Sea Otter Population Remains Stable. (n.d.). Retrieved December 28, 2018, from https://pasoroblesdailynews.com/central-coast-sea-otter-population- remains-stable/87089

Doroff, A. & Burdin, A. 2015. Enhydra lutris. The IUCN Red List of Threatened Species 2015: e.T7750A21939518. http://dx.doi.org/10.2305/IUCN.UK.2015- 2.RLTS.T7750A21939518.en

Page | 19

Etkind, A. (2011). Barrels of fur: Natural resources and the state in the long history of Russia. Journal of Eurasian Studies, 2(2), 164-171. doi:10.1016/j.euras.2011.03.007

Hall, K. R., & Schaller, G. B. (1964). Tool-Using Behavior of the California Sea Otter. Journal of Mammalogy, 45(2), 287-298. doi:10.2307/1376994

Hatfield, B. B., Ames, J. A., Estes, J. A., Tinker, M. T., Johnson, A. B., Staedler, M. M., & Harris, M. D. (2011). Sea otter mortality in fish and shellfish traps: estimating potential impacts and exploring possible solutions. Endangered Species Research, 13(3), 219- 229. doi:10.3354/esr00327

Jessup, D., Miller, M., Ames, J., Harris, M., Kreuder, C., Conrad, P., & Mazet, J. K. (2004). Southern Sea Otter as a Sentinel of Marine Ecosystem Health. EcoHealth, 1(3), 239- 245. doi:10.1007/s10393-004-0093-7

Jessup, D. A., Miller, M. A., Kreuder-Johnson, C., Conrad, P. A., Tinker, M. T., Estes, J., & Mazet, J. A. (2007). Sea otters in a dirty ocean. Journal of the American Veterinary Medical Association, 231(11), 1648-1652. doi:10.2460/javma.231.11.1648

Kannan, K., Guruge, K. S., Thomas, N. J., Tanabe, S., & Giesy, J. P. (1998). Butyltin Residues in Southern Sea Otters (Enhydra lutris nereis) Found Dead along California Coastal Waters. Environmental Science & Technology, 32(9), 1169-1175. doi:doi:10.1021/es970914u

Kenyon, K.W. (1969) The Sea Otter in the Eastern Pacific Ocean. North American Fauna, 68, 1 – 352. https://doi.org/10.3996/nafa.68.0001

Knickmeyer, E. (2018, May 17). Sea otters rebound but struggle to regain historic range.

Page | 20

Retrieved December 28, 2018, from https://www.570news.com/2018/05/17/returning-otters-to-undersea-world- failing-in-their-absence/

Kreuder, C., Miller, M. A., Jessup, D. A., Lowenstine, L. J., Harris, M. D., Ames, J. A., . . . Mazet, J. A. (2003). Patterns of Mortality in Southern Sea Otters. Journal of Wildlife Diseases, 39(3), 495-509.

Larson, S., Jameson, R., Etnier, M., Jones, T., Hall, R. (2012). Genetic diversity and population parameters of sea otters, Enhydra lutris, before fur trade extirpation from 1741- 1911. PLoS ONE, 7(3), e32205. doi:10.1371/journal.pone.0032205

McKie, R. (2016, July 10). How sea otters help save the planet. Retrieved December 27, 2018, from https://www.theguardian.com/environment/2016/jul/10/sea-otters- global-warming-trophic-cascades-food-chain-kelp

Miller, M. A., Kudela, R. M., Mekebri, A., Crane, D., Oates, S. C., Tinker, M. T., . . . Jessup, D. A. (2010). Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters. PLoS ONE, 5(9), 1-11. doi:10.1371/journal.pone.0012576

Mission. (n.d.). Retrieved December 28, 2018, from http://www.otterproject.org/

Monson, D. H., Doak, D. F., Ballachey, B. E., Johnson, A., & Bodkin, J. L. (2000). Long-term impacts of the Exxon Valdez oil spill on sea otters, assessed through age-dependent mortality patterns. Proceedings of the National Academy of Sciences, 97(12), 6562- 6567. doi:10.1073/pnas.120163397

Nicholson, T. E., Mayer, K. A., Staedler, M. M., Fujii, J. A., Murray, M. J., Johnson, A. B., . . .

Page | 21

Houtan, K. S. (2018). Gaps in kelp cover may threaten the recovery of California sea otters. Ecography, 41(11), 1751-1762. doi:10.1111/ecog.03561

Programs. (n.d.). Retrieved December 28, 2018, from http://www.otterproject.org/

Sea Otter. (2018, September 21). Retrieved December 27, 2018, from https://www.nationalgeographic.com/animals/mammals/s/sea-otter/

Sea Otter Conservation. (n.d.). Retrieved December 28, 2018, from

http://www.aquariumofpacific.org/exhibits/otters/sea_otter_conservation

Sea Otter Habitat. (n.d.). Retrieved November 14, 2018, from http://bioweb.uwlax.edu/bio203/s2008/bluske_brit/Habitat.htm

Sharifi, M., & Vaissi, S. (2014). Captive breeding and trial reintroduction of the Endangered yellow-spotted mountain newt Neurergus microspilotus in western Iran. Endangered Species Research, 23(2), 159-166. doi:10.3354/esr00552

Sources and Solutions. (2017, March 10). Retrieved December 26, 2018, from https://www.epa.gov/nutrientpollution/sources-and-solutions

Southern Sea Otter (n.d.). Retrieved December 27, 2018 from https://www.fws.gov/ventura/endangered/species/info/sso.html

Southern Sea Otters. (n.d.). Retrieved December 28, 2018, from https://www.aquariumofpacific.org/conservation/research/southern_sea_otters

Southern Sea Otters. (n.d.). Retrieved October 3, 2018, from

Page | 22

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

Stephens, T. (2010, September 10). Sea otter deaths linked to toxin from freshwater bacteria. Retrieved December 18, 2018, from https://news.ucsc.edu/2010/09/otter-toxin.html

Thometz, N. M., Tinker, M. T., Staedler, M. M., Mayer, K. A., & Williams, T. M. (2014). Energetic demands of immature sea otters from birth to weaning: Implications for maternal costs, reproductive behavior and population-level trends. Journal of Experimental Biology, 217(12), 2053-2061. doi:10.1242/jeb.099739

Tinker, M. T., Hatfield, B. B., Harris, M. D., & Ames, J. A. (2015). Dramatic increase in sea otter mortality from white sharks in California. Marine Mammal Science, 32(1), 309- 326. doi:10.1111/mms.12261

U.S. Department of Interior. (2004). Administration of the Marine Mammal Protection Act of 1972, U.S. Department of the Interior, January 1, 1992 to December 31, 1992 (pp. I-52).

U.S. Fish and Wildlife Service. 2003. Final Revised Recovery Plan for the Southern Sea Otter

(Enhydra lutris nereis). Portland, . xi + 165 pp.

Page | 23

Appendix

Figure 1. Kelp forests underwater along the coast of California, Cannon, J.C. (2012).

Page | 24

Figure 2. This distribution map shows the historic and current ranges of the Southern sea otters before and after the fur trade, respectively, Knickmeyer, E. (2018).

Page | 25

Figure 3. A Southern sea otter sleeping in the protection of kelp, Cannon, J.C. (2012.).

Figure 4. Sea otter mother carrying her pup, Southern Sea Otters, Monterey Aquarium (n.d.).

Page | 26

Figure 5. A Southern sea otter rescued and cared for, Southern Sea Otters, Monterey Aquarium (n.d.).

Page | 27