February 5, 2018 Biodiversity Written by Sara Slavikova
10 endangered marine mammals in the world
In Native American folklore, whales are depicted

as guardians of oceans. They are a symbol of wisdom and considered spiritual animals. These gentle giants were highly respected and just the mere sighting of a whale meant good luck [1]. While our ancestors believed that whales are invincible, we know today that they are, just like many other marine mammals, struggling to survive.

Marine mammals play a vital role in the balance of marine ecosystems. Strong ecosystems rely on maintaining a healthy and diverse assemblage of plants and animals. Marine mammals keep populations in check and create habitats for other underwater inhabitants. Given their importance in the ecosystem, all species of marine mammals are protected under the United States Marine Mammal Protection Act (MMPA). Some of them are also listed under the Endangered Species Act (ESA) and the international Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Despite these legal protections, many marine species are currently endangered due to a multitude of factors, such as the ruthless behavior of fishermen and loss of habitat. These animals include species of whales, seals and porpoises, with the poor Vaquitas porpoise literally dying out as you are reading this article.


The most endangered marine mammals swimming in the world’s ocean


1. Vaquita

The Vaquita is a small member of the porpoise family and resides in the waters off the coast of Baja California in Mexico. This species is listed as critically endangered due to a decline in population of 92% (!) since 1997. According to the most recent report of the International Committee for the Recovery of the Vaquita, only 30 vaquitas are currently swimming in the ocean [2].

Their already low numbers are decreasing rapidly, and it is likely that by 2018 the species will go extinct [3].

The main reason of such a sad turn of events for these timid porpoises has been the continued illegal fishing of the critically-endangered Totoaba, a highly-prized fish in Chinese medicine, which shares the same habitat with Vaquita. Other threats are also closely connected to human activity. They include pesticide exposure and loss of habitat [4].

2. Hawaiian Monk Seal

If the name doesn’t give it away, this species of seal calls the pacific waters of the Northwest Hawaiian Islands home. Hawaiian monk seals are one of the rarest marine mammals on earth and very often they are the innocent victims of humans, being both hunted or trapped in fishing nets or other human debris. Their population has been continuously declining since 1983. In 2011, the number of mature animals was 632 and 577 babies [5].

Even when not taking into account accidental trapping in fishing gear, the number of threats for these solitary animals still remains disproportionately high. Due to changing conditions, their food sources are thinning, and global sea rise claims their resting and reproducing habitat. Pups often face attacks by mature males or become an easy prey for sharks.

3. Steller Sea Lion

The Steller Sea Lion inhabits the waters of the Northern Pacific Ocean. Intentional culling on the coasts of Alaska and Canada has led to their population dropping by nearly 70% between 1977 and 2007.

Luckily, the species is showing signs of recovery. After a new IUCN assessment in 2012, the sea lion was moved from the endangered category to nearly threatened because the probability of extinction is less than 10% in the next 100 years. Their population is currently at 160,000.

Limits to sea lion culling seem to have had a positive effect on their population. Besides intentional killing, these mammals face difficulties coping with habitat changes and reduction of food sources. An additional threat to them is predation by killer whales [6].

A group of Steller Sea Lions in Alaska

A group of Steller Sea Lions in Alaska


4. Australian Sea Lion

This sea lion species is endemic to Australia and has served as a source of food to Australian aboriginals for thousands of years. By the 17th century, these mammals were being hunted beyond sustainable levels. Today, their population is around 6,500, but overall numbers are still decreasing with every generation. According to the IUCN, in 38 years the number of sea lion pups decreased by 57%.

Empirical evidence suggests that these sea lions suffer greatly due to human disturbance and effects associated with pollution. Many animals are caught and die due to bycatch, or are tangled in marine debris [7].

5. Hector’s Dolphin

Found in the waters near northern New Zealand, Hector’s Dolphin is considered to be the smallest marine dolphin in the world. These dolphins are very rare and endangered due to human threats and oftentimes drown as a result of getting trapped in fishing nets. Due to their distribution close to the coast, possibilities to eliminate their exposure to fishing gear remain low. The number of individual animals is 7,381, but their population is rapidly decreasing.

The main threats for these dolphins originate from human activity. Besides being caught as a bycatch, these gentle animals are stressed out by boat encounters and suffer from pollution [8].

6. Sea Otter

Sea otters were once an abundant species, living across the North Pacific rim. But the beginning of commercial hunting throughout the 18th century marked the beginning of otter population decline. By the time their endangered status was acknowledged by the International Fur Seal Treaty in 1911, there were less than 2,000 animals left.

Even though sea otters have recovered since then, currently reaching nearly up to 90,000 animals in Alaska, the overall population numbers are still shrinking. Possible causes are linked to killer whale predation and human activity. Severe pollution is one of the strong contributors of their disappearance.

The Exxon Valdez oil spill alone claimed the lives of at least 3,000 sea otters.

Ocean acidification and climate change related stress are also likely a cause of their ongoing failure to thrive [9].

Sea otter feeding on sea weed

Sea otter feeding on sea weed


7. Blue Whale

This species of whale can be seen in oceans all over the globe due to its long migratory patterns. It is the largest mammal on earth and it is endangered due to a long history of being commercially hunted. Although their hunting has been banned since 1966, they remain endangered today.

According to estimates, blue whale population ranges from 10,000 to 25,000 animals. While this may seem like a lot, in fact, it is only a fraction of their population size as it was in the beginning of the 20th century, corresponding to just 3-11% of that original population size [10].

Since commercial hunting has stalled, populations seem to be increasing. Although, cases of ship strikes, entanglement in fishing equipment or health issues from plastic waste flooding the ocean still present a significant threat. Some scientists also expressed concern about the future survival of blue whales with climate change affecting their natural habitat [11].

8. Sei Whale

Sharing the same destiny with blue whales, globally distributed Sei whales were extensively hunted in the second half of the 20th century, following the ban on blue whale hunting. Commercial hunting of these unlucky mammals was prohibited in 1980s. In 2002, Japan resumed hunting under scientific permit in the North Pacific, allowing 100 animals to be caught each year [12].

The exact population size of Sei whales is unknown, but according to estimates, it accounts for around 20% of their 1937 population size [12]. Swimming in distant waters, these whales currently face (hopefully for good) a low risk of human-caused danger.

9. Fin Whale

After the blue whale, the fin whale is the second largest mammal in the world, characterized by a distinct ridge behind their dorsal fin. Like other whale species, the fin whale is endangered due to hunting and marine pollution.

Until the outbreak of whale hunting, these worldwide distributed whales were known for being too difficult to catch. After a couple of grueling decades, fin whale hunting was prohibited between 1975 and 1990. A small number of whales is allowed to be caught in Greenland every year as part of native legacy.

The number of remaining individuals is unknown due to insufficient data. IUCN projections suggest that these large mammals are currently without any significant threats and their populations are recovering [13].

10. Beluga whale

Known for returning every year to the same estuary, Belugas are an easy prey for hunters. This is one of the main reasons why a subpopulation of Beluga whales inhabiting the Cook Inlet, Alaska, has declined to merely 375 animals in 2004, and is considered to be critically endangered.

Although, the total number of these mammals inhabiting Arctic waters is 150,000, information about some subpopulations is missing. This raises questions as to whether these mammals are thriving or striving.

The subsistence hunting in Alaska, Canada and Greenland is the main reason of Belugas’ endangerment. Climate change in the Arctic is also suspected to have taken its toll by changing water properties and allowing pollutants seep into the ocean. Furthermore, melting sea ice opens ship routes through the north, which increases noise pollution in previously less disturbed waters [14].


Although not part of the top ten, other notable endangered (or previously endangered) marine mammals include the Florida manatee, the humpback whale and the Fraser’s dolphin. Many of these species have declined in numbers due to human negligence. When on or near the ocean, it is important to remember that the ocean is home to many species that do not benefit from our presence. Maintaining the health of these species is important for preserving the health of the ecosystem and the ocean as a whole.



[1] http://www.native-languages.org/legends-whale.htm
[2] http://www.marinemammalcenter.org/science/Working-with-Endangered-Species/vaquita.html
[3] https://goo.gl/g3uAsn
[4] http://www.iucnredlist.org/details/17028/0
[5] http://www.iucnredlist.org/details/13654/0
[6] http://www.iucnredlist.org/details/8239/0
[7] http://www.iucnredlist.org/details/14549/0
[8] http://www.iucnredlist.org/details/4162/0
[9] http://www.iucnredlist.org/details/7750/0
[10] http://www.iucnredlist.org/details/2477/0
[11] https://phys.org/news/2011-07-ocean-garbage-whales.html
[12] http://www.iucnredlist.org/details/2475/0
[13] http://www.iucnredlist.org/details/2478/0
[14] http://www.iucnredlist.org/details/14549/0