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Dolphins

Earth Platform > Animals > Marine Life > Dolphins
Every seven years, half of all dolphins in captivity die from marine pollution, habitat degradation, harvesting, low frequency sonar, entrapment in fishing gear and other stress-related illnesses. Luckily, a number of countries have now stopped or reduced the capture of wild dolphins, and knowledge and conditions are vastly improving. However, there are still many countries where conditions for captive dolphins are well below standards.
 

Dolphins

A lot of dolphins die in fisheries. In the North Sea alone, an estimated 10,000 harbour porpoises are killed in fishing gear each year.  In recent years there have been gear modifications  that make it possible for the dolphins, to escape once a fishingnet is closed. Not every country has made these modifications mandatory yet, so dolphins are still killed in this fishery. The dolphins killed in fishery are mainly common dolphins, spotted dolphins and spinner dolphins. Occasionally other species, including bottlenose dolphins, are caught as well, but their numbers are lower.

dolphinsEspecially in coastal areas, marine mammals are often disturbed by human activities. Collisions with boats and jet skis have already resulted in severe traumas and even deaths of marine mammals, including dolphins. Also, boat traffic in areas where dolphins usually rest or forage can disrupt their normal behaviour. The seemingly harmless human behaviour, such as swimming in areas where dolphins naturally rest, can result in disturbance and changes in behaviour. In a bay in Hawaii for example, where spinner dolphins came to rest, the increase in swimmers, has resulted in the dolphins leaving the bay. They had to find another resting area.

Dolphins are very acoustically oriented animals. With their natural sonar, they rely heavily on sound for their orientation, navigation and communication with other dolphins. Since the last century, the increase in boat traffic around the globe has resulted in a considerable increase in noise in the world's oceans. This has a negative effect on dolphin and whale navigation and communication. 

 

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Dolphins in the news

Dolphins and Whales News -- ScienceDaily

North Atlantic right whales decline confirmed: 458 remaining - Marine biologists have developed a new model to improve estimates of abundance and population trends of endangered North Atlantic right whales, which have declined in numbers and productivity in recent years. Between 1990 and 2010 abundance increased to 482 animals, but since 2010 the numbers have declined to 458 in 2015, with 14 known deaths this year.
Paleontologist aids in new discovery 33 years after finding fossil - The fossilized plesiosaur Sankar Chatterjee found in 1984 is giving scientists a new understanding of convergent evolution between reptiles and mammals.
Tracking down the whale-shark highway - Researchers recently discovered that whale sharks in the Eastern Tropical Pacific follow fronts -- the dynamic boundaries between warm and cold ocean waters.
Peptide mass fingerprinting can identify whale species based solely on their baleen - Peptide mass fingerprinting accurately identified 10 species of whales from their baleen alone, according to a new study.
Fossil whales' teeth shows what ferocious predators they were - The feeding habits of the whale -- the world's biggest animal -- have evolved to filter feeding, shows new international research. Ancient whales appear to have been ferocious predators, investigators explain.