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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

Ocean giant gets a health check: Combination blood, tissue test reveals whale shark diets - Whale sharks, the world's largest fish, likely endure periods of starvation and may eat more plants than previously thought, according to the first results of a new health check. Ocean scientists now have a powerful, simple tool to discover the diets, migrations, and conservation needs of this endangered species.
Far-ranging fin whales find year-round residence in Gulf of California - Researchers from Mexico and the United States have concluded that a population of fin whales in the rich Gulf of California ecosystem may live there year-round -- an unusual circumstance for a whale species known to migrate across ocean basins.
15-meter-long ancient whale Basilosaurus isis was top marine predator - The stomach contents of ancient whale Basilosaurus isis suggest it was an apex predator, according to a new study.
Giant singers from neighboring oceans share song parts over time - Singing humpback whales from different ocean basins seem to be picking up musical ideas from afar, and incorporating these new phrases and themes into the latest song, according to a newly published study that's helping scientists better understand how whales learn and change their musical compositions.
Groups of pilot whales have their own dialects - A new study has found that short-finned pilot whales living off the coast of Hawai'i have their own sorts of vocal dialects, a discovery that may help researchers understand the whales' complex social structure.