Earthplatform.com

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. 

 

More about:

Turtles are one of the world's oldest animals. Now they are driven into extinction by pollution and hunting.
Commercial and 'scientific' whaling, as well as water pollution, still drives whales into an ongoing struggle for survival.

Dolphins in the news

Dolphins and Whales News -- ScienceDaily

Narwhals' acoustic behavior described using audio tagging - The clicking, buzzing and calling behavioral patterns of elusive East Greenland narwhals have been described thanks to in-depth recordings.
Large-scale whaling in north Scandinavia may date back to 6th century - The intensive whaling that has pushed many species to the brink of extinction today may be several centuries older than previously assumed.
Proactive conservation management strategy urged for North Atlantic right whale - Marine ecologists urge a more proactive conservation management strategy for the North Atlantic right whale.
Secret to whale shark hotspots - A study has uncovered the secret to why endangered whale sharks gather on mass at just a handful of locations around the world.
In male dolphin alliances, 'everybody knows your name' - It's not uncommon in dolphin society for males to form long-lasting alliances with other males, sometimes for decades. Now, after studying bottlenose dolphins in Shark Bay, Australia, for more than 30 years, researchers find that these males retain individual vocal labels rather than sharing a common call with their cooperative partners.