From coraldigest
Revision as of 03:39, 13 April 2016 by AMcDarris (talk | contribs) (On Ecosystems)
Jump to: navigation, search

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

The extinction of marine mammals is, in most cases, collateral damage that results from over-exploitation of marine resources and ecosystems. Although animals such as dolphins, otters, and seals suffer due to the disruption of trophic levels, the entire ecosystem in which that animal inhabits does as well.

When trophic levels are disrupted by the world's fisheries in the form of overfishing. By capturing huge amounts of fish and essentially removing the energy and nutrients that those fish provide from the ecosystem, humans are causing changes to energy pathways and the amount of food available to other organisms in the environment. For many marine mammals, overfishing means that major food sources become either scarce or nonexistent. This causes a decrease in the numbers of these mammals -- since less food means a smaller population of predators -- and an influx in species that the fish would have eaten.

Pollution and habitat destruction can also alter an ecosystem and result in the dwindling of marine mammal populations. For example, the theoretical decrease in population of sea urchin populations via pollution could spell doom for sea otter populations due to that source of food being cut off.

Connection to Coral Reefs

A major factor in the endangerment and extinction of species is the loss of habitat. Considering that coral reefs are one of the biodiverse regions on the planet, it should not come as a surprise that the loss of 40 percent of reefs worldwide has also resulted in the decrease of marine mammals and other species that rely on reefs either for food sources, habitat, or breeding grounds.

Additionally, there is a direct relationship between the abundance of coral and the abundance of coral dwelling fish. When coral reef ecosystems collapse, it causes a disruption through the trophic levels; if there are less fish, there are going to be less predators -- such as seals and dolphins -- as well.


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