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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

Baleens read like a whale's history book - Chemically analyzing sequential samples from the baleen of dead whales makes it possible to read not only the history of the diet, but also the migration route of the animals. In a new study, researchers present their results of a novel way of analyzing nitrogen isotopes in animal tissue.
Forty percent of North Atlantic right whale population using Gulf of Saint Lawrence as seasonal habitat - A new study confirms that the Gulf of St. Lawrence is an important habitat for a large proportion of the endangered North Atlantic right whale population.
Whales are more important ecosystems engineers than previously thought - Research on whale feeding highlights how the precipitous decline of large marine mammals has negatively impacted the health and productivity of ocean ecosystems.
Reducing vessel activity key to southern resident killer whale survival - Reducing ship speed and noise levels would increase the probability that endangered West Coast southern resident killer whales will spend more time hunting for Chinook salmon, a new study has found.
Ancestors of whale sharks in Panama may come from distant waters - Genetic population connectivity study of the endangered whale shark in Pacific Panama provides important baseline data for conservation efforts.