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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

Humpback whale population on the rise after near miss with extinction - A new study finds that the western South Atlantic humpback population has grown to 25,000 whales. Researchers believe this new estimate is now close to pre-whaling numbers.
Stranded whales detected from space - A new technique for analysing satellite images may help scientists detect and count stranded whales from space. Researchers tested a new detection method using Very High Resolution (VHR) satellite images of the biggest mass stranding of baleen whales yet recorded. It is hoped that in the future the technique will lead to real-time information as stranding events happen.
Hush, little baby: Mother right whales 'whisper' to calves - A recent study explores whether right whale mother-calf pairs change their vocalizations to keep predators from detecting them.
Scientists uncover genetic similarities among species that use sound to navigate - Insect-eating bats navigate effortlessly in the dark and dolphins and killer whales gobble up prey in murky waters thanks in part to specific changes in a set of 18 genes involved in the development of the cochlear ganglion -- a group of nerves that transmit sound from the ear to the brain, according to a new study.
Researchers use drones to weigh whales - Researchers have devised a way to accurately estimate the weight of free-living whales using only aerial images taken by drones.