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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

Right whales threatened by planned seismic surveys along Mid- and Southeastern Atlantic seaboard, say scientists - A series of seismic surveys for oil and gas planned for the mid- and southeastern Atlantic coastal areas of the United States pose a substantial threat to one of the world’s most endangered whale species, according to a group of renowned marine mammal scientists urging a halt to the surveys in a statement released today.
Fetal and newborn dolphin deaths linked to Deepwater Horizon oil spill - Scientists have finalized a study of newborn and fetal dolphins found stranded on beaches in the northern Gulf of Mexico between 2010 and 2013. The study team identified substantial differences between fetal and newborn dolphins found stranded inside and outside the areas affected by the 2010 Deepwater Horizon oil spill.
Architecture of the sperm whale forehead facilitates ramming combat - A new study addresses a controversial hypothesis regarding the potential ramming function of the sperm whale's head. This hypothesis was instrumental in inspiring Herman Melville to write the novel Moby Dick but its mechanical feasibility had never been addressed.
Slow path to recovery for southern right whales - The first population assessment since the end of the whaling era reveals that New Zealand southern right whales have some way to go before numbers return to pre-industrial levels. Scientists used historic logbook records from whaling ships and computer modelling to compare population numbers.
New maps reduce threats to whales, dolphins - Biologists have created highly detailed maps charting the seasonal movements and population densities of 35 species of whales, dolphins and porpoises -- many of them threatened or endangered -- in US Atlantic and Gulf waters. The maps give government agencies and marine managers better tools to protect these highly mobile animals and guide ocean planning, including decisions about the siting of wind energy and oil and gas exploration along US coasts.