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Extinct Marine Mammals

Conditions that alter marine mammal environment can stress and bottleneck species, leading to extinction through many possible causes

Past Extinctions

  • Basilosaurus (Gingerich)
    • Thought to be reptile, yet was discovered to be a prehistoric whale
    • very large and primitive blue whale ancestor
  • Caribbean Monk Seal (King)
    • closely related to Hawaiian and Mediterranean Monk Seals
    • overhunting for oil, overfished food source
    • Extinct about 1986, last sighted near Jamaica in 1952(King)
  • Japanese Sea Lion (Aurioles)
    • extinct in 1970s
  • Baiji (Fisheries)
    • Considered to be Functionally Extinct


  • Coral Bleaching (IRD)
  • Increase in ocean temperatures
  • increased water turbidity
  • overfishing/overexploitation
  • predatory inflation


On Humans

• Overexploitation seems to be the main issue – loss of fish from overfishing and poor practices can destroy ways of life, jobs, industries, etc. (Read)

• Marine mammals are often caught as bycatch

• Unregulated harvest

• new and innovative solutions to this problem are required to take account of the socioeconomic conditions experienced by fishermen” (Read)

• Issue of regulation versus deregulation – looking at pros and cons of regulation seeing as it costs a lot, but is significant in saving a species (Read)

o Regulation = politically unpopular (Read)

• Poverty and the collapse of other industries can lead to abrupt changes in local fishing conditions – may start to prey on marine mammals once their value as food and bait is noticed (Read)

o Unregulated and usually unsustainable (Read)

o Peruvian dolphins; anchovy fisheries collapsed so people started hunting dolphins; led to depletion in population (Read)

On Ecosystems

• World’s fisheries are not only impacting marine mammals, but the trophic structure as well – by capturing huge amounts of fish they are causing changes in energy pathways and species numbers (Merritt)

o Affect marine mammals adversely

• Loss of biodiversity/ decline in mammals can cause population imbalances in other species (Munday)

Connection to Coral Reefs

• Lots of extinctions/endangerment is caused by loss of habitats – coral reefs have declined 40 percent world wide (Zimmer)

o Partly a result of global warming (Zimmer)

• Loss of coral due to bleaching/global warming have changed the structure of coral reef ecosystems and communities – lead to changes in the fish communities, which lead to more changes through the trophic levels (Munday)

• Direct relationship between abundance of coral and abundance of coral dwelling fish (Munday)


Oceans, unlike terrestrial ecosystems, are still mostly intact. Marine mammal populations could bounce back if they're taken proper care of, which involve the implementation of regulation, community outreach, and more sustainable fishing.

What does make the prevention of extinctions more difficult, however, it is much more difficult to track the health of ocean creatures and ecosystems than it is for terrestrial ones. This means that there is a fair amount of uncertainty in the states of certain populations of endangered marine mammals, which could make the creation of laws difficult if not much is known about the current state of certain species.

An important tactic in preventing the further endangerment and extinction of marine mammals is the regulation of fisheries. Mammals such as dolphins often become entangled in nets, and other creatures such as manatees and whales can be snared by loose pieces of nets. The regulation of fisheries seems to be an important theme in ensuring the health of marine ecosystems, but it is doubly important for the sustainability of marine mammals.

Public programs can also be implemented to raise public and community awareness. For example, people can become more aware of the plight of the manatee and their sour relationship with motor boats. (In 2009, 97 manatees were killed by boat collisions.) If boaters are aware of what type of habitat manatees live in, and aware of the situation in general,they would be careful while boating through marshy areas where manatees are known to live. Public awareness can also spur legislation to provide protective areas or enforce regulation.

Cutting back on carbon emission is also essential in slowing extinctions.

According to a 2015 New York Times article, the oceans are facing mass extinctions of species of all kinds. It's not irreversible yet, and there's still time for humans to slow and possibly stop the damage. However, this relies on limiting the exploitation of marine resources.


Institut de Recherche pour le Développement, Paris (IRD). (2008, November 3). Coral Bleaching Disturbs Structure Of Fish Communities. ScienceDaily. Retrieved February 29, 2016 from www.sciencedaily.com/releases/2008/10/081028132106.htm

Fisheries, NOAA. "Chinese River Dolphin / Baiji (Lipotes vexillifer)  :: NOAA Fisheries". www.fisheries.noaa.gov. Retrieved 29 February 2016.

Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group) (2008). Zalophus japonicus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 29 February 2016.

King, J. (1956). "The monk seals (genus Monachus)". Bull. Brit. Mus. (Nat. Hist) Zool. 3: 201–256.

Gingerich, Phillip D. 2007. Basilosaurus Cetoides. Encyclopedia of Alabama. Available from: [1]

Les Kauffman and Kenneth Mallory (eds).1984. Grew out of a public lecture series entitled 'Extinction: saving the sinking ark,' held in Boston, Massachusetts, at the New England Aquarium during the fall of 1984.

Read AJ. 2008. The Looming Crisis: Interactions between Marine Mammals and Fisheries Journal of Mammalogy. Journal of Mammalogy 89:541–548.

Munday PL. 2004. Habitat loss, resource specialization, and extinction on coral reefs Global Change Biology. Global Change Biology 10:1642–1647.

Zimmer C. 2015. Ocean Life Faces Mass Extinction, Broad Study Says the New York Times [Internet]. the New York Times [Internet]. Available from: http://www.nytimes.com/2015/01/16/science/earth/study-raises-alarm-for-health-of-ocean-life.html?_r=0