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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

How long does a whale feed? New data gives insight into blue and fin whale behavior - Researchers using electronic tags were able to monitor blue and fin whales off the coast of Southern California over multiple weeks, providing new insight into the feeding behaviors of the two largest whale species.
New whale species discovered along the coast of Hokkaido - A new beaked whale species Berardius minimus, which has been long postulated by local whalers in Hokkaido, Japan, has been confirmed.
Modeling predicts blue whales' foraging behavior, aiding population management efforts - Scientists can predict where and when blue whales are most likely to be foraging for food in the California Current Ecosystem, providing new insight that could aid in the management of the endangered population in light of climate change and blue whale mortality due to ship strikes.
New research helps predict locations of blue whales so ships can avoid them - A new model based on daily oceanographic data and the movements of tagged whales has opened the potential for stakeholders to see where in the ocean endangered blue whales are most likely to be so that ships can avoid hitting them.
Narwhals and belugas can interbreed - A team of researchers has compiled the first and only evidence that narwhals and beluga whales can breed successfully. DNA and stable isotope analysis of an anomalous skull from the Natural History Museum of Denmark has allowed researchers to confirm the existence of a narwhal-beluga hybrid.