ExtinctMammals

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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

Causes

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

Effects

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)

Prevention

• Oceans, unlike terrestrial ecosystems, are still mostly intact – could easily bounce back if they’re taken proper care of (Zimmer)

o Somewhat uncertain about this though – it’s much harder to track the health of ocean mammals than it is of terrestrial ones (Zimmer)

• Not irreversible yet (Zimmer)

• Regulations for overharvesting of fish – mammals such as dolphins often become entangled in nets and will be benefited by such regulation (Zimmer)

• Still time for humans to stop the damage with effect programs that “limit the exploitation of the oceans” (Zimmer).

• Slowing extinction = cutting back on carbon emissions (Zimmer)

References

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

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