Marine Biology

PINNIPEDS

            Unlike the cetaceans and sirenians, the pinnipeds have to go to the shore to reproduce. Sea-lions have external ears and their hind flippers are turned forward under the body in the direction of the heads. They feed on fish, mollusks, crustaceans and sea birds. Seals are distinguished by the lack of external ear and their limbs are turned backwards.They are  important as a marine fishery resource and are mainly serving as a food source for the humans of the polar regions.

           They are predators  and usually like to hunt for fish and squid. Pinnepeds have blubber, which a thick layer of fat under the skin that helps then to remain  warm. They have streamlined bodies and flippers are used for swimming. Most of them live in cold water, but pinnipeds have to breed on land.  Seals

           These are the largest group of pinnipeds. They swim  primarily by using their rear flippers and on  land, they  use their front flippers to walk. The elephant seal is the largest  of all the pinnipeds.

Sea lions

They can also use their rear flippers to walk, allowing them to use all four limbs for walking on land.

Walrus

    Walruses have a pair of tusks projecting down from their mouth .

Sea otter

Sea otters have dense, dark brown fur and are carnivorous animals. Sea otters lack blubber, but their fur keeps them insulated from the cold air. Sea otters are threatened species.  Sea otters are polygynous: males tend to defend large territories that encompass the ranges of several females. Sea otters feed on or near the bottom in shallow waters (often in kelp beds). Major prey items are benthic invertebrates such as abalones, sea urchins, and rock crabs. However, sea otters also eat other shellfishes, cephalopods, and sluggish near-bottom fishes.

Polar bear

The single marine species, the polar bear, qualifies as the least aquatic of all marine  mammals.

Polar bears (Ursus maritimus) have dense, white fur and are semi-aquatic carnivorous animals.They are found in the Arctic. They like to feed on seals. Generally, the pelage of polar bears is white, but based  on light and situations they  can appear yellow, light brown, or light grey. The nose and skin are black. The primary diet of polar bears consists of ringed seals, but they also take bearded, harp , and hooded seals, and rarely walruses and white whales. These bears sometimes eat arctic cod and other forms of animal and vegetable matter. Polar bears have a circumpoalr distribution in the Northern Hemisphere.

Sirenians

        Though manatees, dugongs  (sea cows).  resemble whales, they are anatomically different and totally unrelated. They live in shallow seas, bays, estuaries and rivers. These are purely herbivores  and feed mainly on algae and other submerged aquatic vegetations. Manatees occur in the Carribean region, in the shallow waters of West Indies, northern South America and West coast of Africa. Adult manatees attain length of 3-5 meters and weigh about 700 kilos.

          Dugongs are inhabitants of the Indo-Pacific region. They are more marine in habit than manatees and mostly eat larger seaweeds. They are shorter than manatees having only a length of about 3 meters. The sea-cows are the largest of the sirenians, attaining a length of  nearly 8 meters. They differ from sirenians in having no teeth.

• The dugongs were hunted for their flesh and oil which are reported to be very delicious. Dugong oil is very clear and free from any bad  taste. Nearly 50 liters of oil can be obtained from a full- grown dugong. It is known to have high therapeutic value like that of cod-liver oil. Now the sirenians are not a valuable fishery resource now, since the sea-cows have almost been exterminated and the manatees much reduced in number Dugongs are also on the verge of extinction from the shores of many Asian countries.