Sea Otters in Southern California: A Forgotten Extinction


In 350 B.C.E, in his book The Politics Aristotle stated that animals and plants exist for the sake of others, thus portraying what was later defined as the food chain. In his book On Origins of Species (1859), Charles Darwin talked about a “web of complex relations” (p. 58). Later, the concept of ecosystem emerged as a community of interacting organisms and their environment. American ecologist Raymond Lindeman stated that there are trophic levels between organisms, and these are also known as feeding levels and can be pictured as a pyramid, in which every animal is dependent on the organism below to survive. In late 70s, American ecologist Robert Paine proved the hypothesis of trophic cascade, showing how a system can be drastically changed by removing or altering the presence of certain animals, defined as keystone species.  

Sea otters are a keystone species whose presence benefits the whole ecosystem. However, in the 18th century they were eradicated, and consequently the ecosystem was severely disrupted. In order to resolve this problem, we must reintroduce sea otter populations using translocation-based methods and thus restore the previous natural balance.

In the first section of my paper, I am providing some context and historical reasons as to why this species went virtually extinct, why their presence has caused conflicts within the fishing industry, and what has been done in terms of laws and regulations to protect this endangered species. In section 2, I am discussing how southern sea otters are crucial for the health and stability of marine ecosystems and nearshore communities in California, as they allow kelp forests to thrive by eating sea urchins and other herbivores. In section 3, I am explaining the reasons why sea otters are not expanding quickly in southern California, illustrating some of the many factors playing a role in the population growth and expansion of this species. Lastly, I am outlining future steps as part of a necessary conservation program, and I am making suggestions on how to reestablish this species in southern California.  


Section 1 – History: From Eradication to Legal Protection

Sea otters used to occupy a wide territory in the Pacific Ocean, stretching from the northern Japanese archipelago, through the Aleutian Islands, along the coast of North America all the way to Morro Hermoso, in Baja California, Mexico. This species counted between 15,000-20,000 individuals in California before the 18th century fur trade (Lafferty & Tinker, 2014). By the 20th century, hunting triggered a virtual extinction of this species, causing its existence to rely on a small colony of 50 sea otters in Big Sur, California (Shawn et al., 2015). Over time, sea otter populations began to recover and today occupy roughly 13% of their historic range in California, which covers mostly the central coast.

The recovery plan of this marine mammal has been arduous, as the otter expansion to southern California is an issue for the fishing industry and recreational fishing. The absence of this species in southern waters caused a non-natural high abundance of shellfish, especially urchins and abalones, which fisheries exploited throughout the decades. The conflict emerged in the 60s and nowadays fisheries are still an obstacle in the reintegration of this species to their former habitat.

After years of advocacy, activism, and public awareness, the U.S. Fishing and Wildlife Service (USFWS) started a translocation program in 1987. A group of 140 wild sea otters was taken from the central coast to San Nicolas Island, and this area was surrounded by a “no-otter” management zone, strongly requested by the local fisheries. This zone was designed to protect the lucrative fishing companies, as “unrestricted sea otter range expansion could cause the extinction of the now federally endangered white abalone and black abalone, harm precariously low stocks of other abalone species in California, and destroy shellfish fisheries throughout Southern California” (Shawn et al., 2015). If otters crossed into the management zone, they would be removed and taken back to the central coast. Because the population was not growing and many sea otters died during capture, the program was considered a failure and it officially ended in 2012. Although the translocation plan did not bring a rapid population growth immediately, the number of sea otters in San Nicolas Island continues to grow and counts about 80 individuals (Davis et al., 2019).

Sea otters are now protected by law from hunting in the United States, Canada, Russia, and Japan. Specifically in the U.S., they are protected under federal laws such as the United States Marine Mammal Protection Act, and the Endangered Species Act. Their small population size, reduced habitat, and the risk of oil spills were the reasons which pushed USFWS to list southern sea otters as endangered species in 1977. As it appears on the IUCN Red List, sea otters are still considered endangered, and according to the last assessment dated January 2020 the populations are currently decreasing on a global level (Larson et al., 2020).  


Section 2 – Saving the Otters to Save the Whole Ecosystem

Keystone predators are important because they keep a system balanced by regulating the population density and the behavior of prey. Therefore, the removal or alteration of predator populations may change drastically an ecosystem, leading to its breakdown and, in extreme cases, to species extinction. A clear exemplification is the case of Steller’s Sea Cows, marine mammals that used to live in the Bering Strait and went extinct in 1768. What triggered their disappearance seems to be the extensive hunting of sea otters during the fur trade. Because sea otters were not around anymore, urchins began to increase and grazed voraciously on kelp forests. This led to the collapse of kelp beds, where Steller’s Sea Cows would find their food source, and resulted in this species’ extinction. Sea otters, then, are a prime example of a keystone species.

Because the absence of sea otters allows herbivores like sea urchins to expand and increase in the littoral zone, kelps and seagrass deplete at an unnatural pace. In contrast, research shows that the presence of sea otters carries a wide range of positive benefits for the nearshore communities, and “urchins seek refuge in rock cervices and subsist on kelp detritus” (Wilmers et al., 2012) resulting in an increase of biomass of kelp forests.

Kelp forests and seagrass provide habitat to a wide variety of kelp-dependent species like fish and seabirds, and this leads to an increased resilience and biodiversity of the nearshore communities. Another positive effect triggered by the expansion of kelp is major carbon sequestration. In fact, autotrophs need carbon dioxide to grow and produce food for herbivores, and through photosynthesis they convert it to sugar and oxygen, which is then released in the environment. Much of the carbon sequestered by kelps remains for long periods in the deep ocean in the form of marine snow (Gregr et al., 2020), thus providing an equivalent to annual terrestrial soil carbon sequestration. A bigger biomass of kelp may also work as a coastal protector from storm surge and waves, resulting in a controlled shoreline erosion (Davis et al., 2019).

In addition to ecological effects, it is important to mention the economic value of sea otters discussed in a study by Gregr et al. (2020), which may incentivize governments and institutions to protect and reintroduce this marine mammal. The study was conducted in Canada and shows how the increased biodiversity of fish, like the lingcod, resulting from the otters’ presence is predicted to be worth 9.4 million CA$ per year. Gregr et al. (2020) also suggest that the carbon sequestered by the otter-kelp trophic cascade could be sold in the carbon trading market, and another study conducted by Wilmers et al. (2012) reported that this trading could be valued at 205-408 million US$. In addition, sea otters can also generate profits in the tourism industry, and because they attract visitors who are willing to pay for wildlife viewing trips, this may generate 41.5 million CA$ per year (Gregr et al., 2020).


Section 3 – Why Aren’t Southern Sea Otters Expanding Quickly?

In California, the sea otter population can only expand in two directions – either north or south. In this limited spreading configuration, southern sea otters are concentrated along the central coast. A wider range expansion is key to a full recovery of this marine species, and a slow pace in the expansion has led biologists and scientists to question the quality of habitats in California.

First, climate change poses major challenges to marine ecosystems, and these are higher ocean temperature, acidification, and deoxygenation. Warmer waters can negatively influence kelp beds as they wipe them out, leading to the destruction of marine habitats and the decimation of invertebrate populations on which sea otters feed. They also favor the appearance of toxin producing plankton species, harmful algae, and cyanobacterial blooms which have strong effects on the health and life of sea otters (Larson et al., 2020).

In addition to this, the southern region of California is characterized by human densities, which carry the problem of higher pollution and activities in the ocean, such as lucrative fishing that may deplete sea otters’ favorite prey much faster than in other areas. Moreover, sea otters may be fatally affected by fishing gear, in which they have often been found entangled (Shawn et al., 2015).

Although sea otters are predators, they are not at the apex of the food chain. In fact, they can be chased and attacked by other species, like the great white shark. These predations discourage sea otters from abandoning their refuge near the coast, resulting in a limited population growth and range expansion.

Apart from all these external reasons, research proves that sea otter populations do not expand fast due to their reproductive system as well. Sea otters, in fact, aggregate into groups for safety and breeding, only males explore and claim new territories while females begin to arrive only after several years. Moreover, according to Lafferty and Tinker (2014) “additional range expansion slows or stops as local densities build up”, and this reflects the social nature of this species.


Section 4 – Solutions: Rebuilding Sea Otters’ Broken Home

The future of sea otters depends on continuous conservation efforts, such as restoring and protecting coastal habitats, followed by additional translocations to favor sea otters’ recolonization, and constant fieldwork to monitor their conditions. 

Protecting and restoring habitats that may work as refuge from predators is crucial to encourage a rapid sea otter population growth. Estuaries represent the perfect environment for this marine mammal, as they are home to abundant invertebrate communities and seaweed, and they also provide shelter from predators. Restoring estuaries will also have positive impacts on flood management, water filtration, shoreline protection, and it will provide recreational and education opportunities (Hughes et al., 2019)

Translocation programs can facilitate the recolonization of sea otters’ range. Although the San Nicolas Island plan was declared a failure and interrupted in 2012, it shows that the sea otter population is growing. Since the natural range expansion of sea otters is slow and hindered by many aspects discussed in section 3, we can conclude that translocations should be increased, and estuaries could be home to these newly introduced otters. In addition to an increase in number of sea otters, translocations may also help improve the genetic diversity, and they will indirectly restore the conditions of the coastal and marine ecosystems, as it is shown in section 2.

Even though estuaries are home to diverse invertebrates and are rich in seaweed, they are often close to human high-density areas, which may introduce pollutants in the water and adjacent land. So, it is essential to ensure that translocations in estuaries are assisted by restoration and protection plans of the same, or that the targeted locations are not exploited or affected by human activities.

Unfortunately, there are side-effects to the reintroduction, mainly sea otters compete for the same fish populations as fisheries in southern California. This conflict could be solved by providing clear information on the sea otters’ distribution and patterns of consumption, which would help foresee the areas influenced by the otters’ presence. Thanks to this information, the transition to alternatives and other ways of fishing, such as marine mariculture, is encouraged. Furthermore, the increase in biomass of kelp forests, triggered by the presence of sea otters, enhances other types of fish, such as the lingcod, and the lost profits to the fishery may be offset by an increase of this species. 

At this point, it’s clear that conservation efforts and strategies need to be long-term, and researchers must focus on monitoring the status, population trends and distribution, and the causes of mortality of the sea otters. At the same time, research needs to be supported by proactive restoration and protection of identified sites.


Section 5 – Conclusion

We saw that sea otters are a keystone species and that their removal causes cascading effects on the whole ecosystem. So, reintroducing them means to reestablish the natural balance of nearshore communities and coastal ecosystems, but because sea otter populations do not grow nor expand their range quickly, it is important to implement solutions that entail long-term conservation strategies, translocation programs, identification of adequate sites as future homes, and continuous research to monitor the trends and conditions of the southern sea otter.

After contacting an author of the research conducted by Gregr et al. (2020), it’s evident that the problem of sea otters not reclaiming their historical range is not being considered as strongly by the public and the scientific community. The San Diego County is characterized by very few estuaries, but it’s rich in lagoons and wetlands. At the end of my visit at the San Elijo Lagoon Ecological Reserve and Nature Center near San Diego, I could deduce that the habitat cannot be home to sea otters due to its proximity to the railroad and the highway, and due to the absence of kelps and limited amount of seagrass. Despite these complications, there is still hope that studies can identify safe environments for sea otters in southern California in the future.

Because we need this planet to function perfectly to live, we also need to acknowledge that the ecosystem is a machine that works only if all the parts are present and intact. Now, considering the existence of animal species in economic terms and values can incentivize governments and societies to protect, appreciate, and reintegrate these animals, but the ultimate truth is we need to acknowledge that animals and plants have a non-use value, which is simply the benefit we obtain by knowing that a species continues to exist (Cabezas, 2021).

In his book A Sand County Almanac (1949), Aldo Leopold said, “a system of conservation based solely on economic self-interest is hopelessly lopsided” (p. 214). In other words, the presence of sea otters has effects that go beyond the economic dimension; in fact, they sustain and provide for a system of life that our society cannot and has not created itself. Therefore, we need an ethical framework which speaks clear and can connect citizens to better address current issues such as climate change and animal extinction on a deeper level. In other words, our goal must be to ensure that the value of sea otters, just like any other living species, will continue to exist even tomorrow.




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