m.sc marine science

1. Marine Mammals
PATHAN FARHANKHAN I.
M.Sc. SEM : 2
ROLL NO. : 1
DEPARTMENT OF MARINE SCIENCE
M.K.BHAVNAGAR UNIVERSITY 1

2. What is Marine Mammals 
• Mammals that live and feed in the marine (aquatic) environment.
• Marine mammals, which include seals, sea lions, whales, dolphins, porpoises, manatees,
dugongs, marine otters, walruses, and polar bears, form a diverse group of 130 species that
rely on the ocean for their existence.
• The level of dependence on the aquatic environment for existence varies considerably with
species. For example, dolphins and whales are completely dependent on the marine
environment for all stages of their life, where as seals feed in the ocean, but breed on land.
• Approximately 200 million years ago, another group of air-breathing vertebrates, the
mammals, evolved from now-extinct reptiles. 2

3. Group of marine mammals
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• Whales , Dolphins, Porpoises.cetaceans
• manatees and dugongs.Sirenians
• The polar bear, and two species of
sea-otter.
Fissipeds
• seals, sea lion , and walruses.Pinnipeds

4.  Cetaceans (whales , dolphins, and porpoises)
Humpback whale
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5.  Sirenians (manatees and dugongs)
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6.  Pinnipeds (seals, sea lion , and walruses)
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7.  Fissipeds (Polar bear and sea otter)
Polar bear Sea otter
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8. Distribution
• Marine mammals are widely distributed throughout the globe, but their
distribution is patchy and coincides with the productivity of the oceans. Species
richness peaks at around 40° latitude, both north and south.
• Total species range is highly variable for marine mammal species. On average
most marine mammals have ranges which are equivalent or smaller than one-
fifth of the Indian Ocean.
• Marine mammals are widely distributed .
• Abundance and species richness are high in South Sri Lanka coast followed by
Southeastern Arabian Sea (off Kerala – Karnataka).Marine mammals are not
randomly distributed in the world’s oceans.
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10. • Marine mammals have undergone various evolutionary changes to their body
shape and function in order to adapt to their lives in the oceans of the world.
• The cetaceans and some of the pinnipeds show very strong streamlining .
• All Cetaceans and Sirenians have lost their hind limbs and the hind limbs have
been radically modified into flippers in pinnipeds.
• The forelimbs have been modified into flippers in the 3 major groups of marine
mammals, and additionally a dorsal fin has evolved for stability in the Cetaceans.
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11. • Different group of marine mammals have different feeding ecologies.
• Baleen whales are batch feeders ,taking in large amounts of prey and filtering
them from the waters with the finges on inside of their baleen plates.
• The pinnipeds generally feed on fishes and squids although some take primarily
invertebrates such as krill.
• The sirenians are all herbivores and therefore do not need to be particularly fast
to catch prey.
• The sea otter feeds mostly on invertebrates, such as crabs, Sea urchins . otters
often use rocks as tools to break apart the hard shells of their prey. 11

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14. Threats and conservation of marine mammals:-
• 1-Exploitation
• 2-By-catch
• 3-Vessel strikes
• 4-Habitat loss and degradation
• 5-Pollution
• 6-Global climate change
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15. Exploitation
Marine mammals were hunted by coastal aboriginal humans
historically for food and other resources.
Marine mammals have long been highly –prized targets of humans
looking for a good source of food ,furs ,oil, and later a whole host of
other products.
 Commercial whaling is generally a thing , a number of marine
mammals are still subject to direct hunting.
Today, populations of species that were historically hunted, such as
blue whales, and the North Pacific right whale, are much lower
compared to their pre-exploited levels.
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16. By- Catch
By-catch is the incidental capture of
non-target species in fisheries.
 By-catch affects all cetaceans, both
small and big, in all habitat types.
How ever, smaller cetaceans
and pinnipeds are most vulnerable as
their size means that escape once they
are entangled is highly unlikely and
they frequently drown.
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17. Vessel Strikes :
Vessel strikes cause death for a number of
marine mammals, specially whales.
In particular, fast commercial vessels such
as container ships can cause major
injuries or death when they collide with
marine mammals.
 Collisions occur both with large
commercial vessels and recreational
boats and cause injury to whales or
smaller cetaceans.
 The critically endangered northern right
whale is particularly affected by vessel
strikes. 17

18. Pollution:-
Contaminants that are discharged into the
marine environment accumulate in the
bodies of marine mammals when they are
stored unintentionally in their blubber along
with energy.
Noise pollution from anthropogenic
activities is another major concern for
marine mammals.
This is a problem because underwater noise
pollution interferes with the abilities of
some marine mammals to communicate, and
locate both predators and prey. 18

19. Global climate change
Two changes to the global
atmosphere due to anthropogenic
activity threaten marine
mammals.
The first is increases in
ultraviolet radiation due to ozone
depletion, and this mainly affects
the Antarctic and other areas of
the southern hemisphere.
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20. Habitat loss and degradation
Habitat degradation is caused by a
number of human activities. Marine
mammals that live in coastal
environments are most likely to be
affected by habitat degradation and
loss.
Developments such as sewage marine
outfalls, moorings, dredging, blasting,
dumping, port construction,
hydroelectric projects, and aquaculture
both degrade the environment and take
up valuable habitat
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22. Reference
• A Book “Marine Mammals of the world “by Thomas A. Jefferson
,Marc A .Webber, Robert L. Pitman.
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