marine mammals ,Farhankhan pathan

Marine Mammals

PATHAN FARHANKHAN I.M.Sc. SEM : 2ROLL NO. : 1

DEPARTMENT OF MARINE SCIENCEM.K.BHAVNAGAR UNIVERSITY 1

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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.

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Group of marine mammals• Whales , Dolphins, Porpoises. cetaceans

• manatees and dugongs.Sirenians

• The polar bear, and two species of sea-otter.

Fissipeds

• seals, sea lion , and walruses.Pinnipeds

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Cetaceans (whales , dolphins, and porpoises)

Humpback whale

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Sirenians (manatees and dugongs)

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Pinnipeds (seals, sea lion , and walruses)

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Fissipeds (Polar bear and sea otter)

Polar bear Sea otter

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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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Physiological Adaptation• 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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Feeding Ecology• 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.

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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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ExploitationMarine 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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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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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.

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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.

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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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Habitat loss and degradationHabitat 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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Reference

• A Book “Marine Mammals of the world “by Thomas A. Jefferson ,Marc A .Webber, Robert L. Pitman.

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