Journal of Marine Science: Research & Development
Open Access

Marine mammals; Aquatic lifestyle; Commercial hunting; Marine biology

Marine mammals are aquatic creatures that rely on the ocean and other marine ecosystems for their living. They include animals such as adhesive seals, cetaceans, manatees, sea otters and polar bears. They are an informal group, unified only by their reliance on sea circumstances for feeding and survival [1].

Marine mammal alteration to an aquatic lifestyle ranges considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are require water dwellers [2]. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water but need to return to land for predominate activities such as mating, breeding and molting. In contrast, both otters and the polar bear are much less adjusted to aquatic living. The diets of aquatic mammals vary significantly as well; some eat zooplankton, others eat fish, squid, shellfish, or sea-grass, and a few eat other mammals. While the number of aquatic mammals is small compared to those found on land, their roles in different ecosystems are large, especially concerning the preservation of marine ecosystems, through processes including the mandatory of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently pressurized.

Marine mammals were first tracked by aboriginal peoples for food and other resources. Many were also the quarry for commercial industry, leading to a sharp decline in all populations of exploited individuals, such as whales and seals [3]. Commercial hunting led to the destruction of Steller's sea cow, sea mink, Japanese sea lion and the Caribbean monk seal. After commercial hunting ended, some individuals, such as the gray whale and northern elephant seal, have recoil in numbers; conversely, other species, such as the North Atlantic right whale, are majorly endangered [4].

A large proportion of all life on Earth lives in the marine system. The exact size of this large proportion is unspecified, since many ocean species are still to be discovered. The ocean is a complex threedimensional world covering approximately 80% of the Earth's surface area. The habitats researches in marine biology include everything from the tiny layers of surface under water in which organisms and abiotic items may be trapped in surface tension between the ocean and environment, to the depths of the aquatic trenches, sometimes 11000 meters or more beneath the surface of the ocean. Specific habitats include estuaries, coral reefs, kelp forests, sea grass meadows, the neighbouring of seamounts and thermal vents, tide pools, muddy, sandy and rocky bottoms, and the open marine (pelagic) zone, where solid objects are rare and the surface of the water is the only visible margins. The organism studied varies from microscopic phytoplankton and zooplankton to huge cetaceans whales 25-35m (79-110 feet) in length. Marine ecology is the study of how marine organisms interlinked with each other and the environment.