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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

Shifting presence of North Atlantic right whales tracked with passive acoustics - A new study confirms what marine mammal researchers have suspected for a while: right whales use nearly the entire eastern seaboard during the winter, and they move around a lot more than was previously thought. How long they spend in some areas of their range has also changed in recent years.
Right whales, already an endangered species, may face a dim future - Researchers show that right whales, already an endangered species, may face a dim future.
Weak social ties a killer for male whales - Male killer whales are more likely to die if they are not at the center of their social group, new research suggests.
Whales and dolphins have rich 'human-like' cultures and societies - Whales and dolphins (cetaceans) live in tightly-knit social groups, have complex relationships, talk to each other and even have regional dialects -- much like human societies. A major new study has linked the complexity of Cetacean culture and behavior to the size of their brains.
'Killer' toothaches likely cause misery for captive orca: Whales chew concrete and steel tank surfaces - An international research team has undertaken the first in-depth investigation of the teeth of captive orca (killer whales) and have found them a sorry state, which raises serious concerns for these majestic mammals' overall health and welfare.