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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

Shedding light on the origin of the baleen whale - The origin of filter feeding in baleen whales -- the largest animal known to have ever existed -- is now better understood, thanks to research on 'Alfred' the 25- million-year-old fossilized whale skull.
New forecast tool helps ships avoid blue whale hotspots - Scientists have long used satellite tags to track blue whales along the West Coast, learning how the largest animals on the planet find enough small krill to feed on to support their enormous size. Now researchers have combined that trove of tracking data with satellite observations of ocean conditions to develop the first system for predicting locations of blue whales off the West Coast. The system, called WhaleWatch, produces monthly maps of blue whale "hotspots" to alert ships where there may be an increased risk of encountering these endangered whales.
Teenage male whale sharks don’t want to leave home - Researchers have completed a huge photo-identification study to assess the seasonal habits of whale sharks in the tropics. They were surprised to discover that the male juveniles didn't seem to venture too far from home.
Impacts of climate warming, declining sea ice on Arctic whale migration - Declines in the Arctic sea ice are arguably the most dramatic evidence of the effects of current climate warming on ocean systems. While sea ice is perhaps the most defining feature of the habitat of Arctic whales, the relationship between them and sea ice is still largely a mystery, and there is increasing concern over how these species will adapt to climate related changes in sea ice.
Acoustic buoy now detecting rare and endangered whales in New York Bight - An acoustic buoy making its first near real-time detections of two rare great whale species in the New York Bight, including the highly endangered North Atlantic right whale.