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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

Did mosasaurs hunt like killer whales? - Researchers have examined the youngest-ever specimen of tylosaur ever found. Like orcas, mosasaurs might have used their bony noses to strike prey.
Evolutionary 'arms race' -- how dolphins and whales fight disease threats - A groundbreaking study reveals how dolphins, whales and other cetaceans compete for survival in an evolutionary 'arms race' with changing pathogenic threats like mercury and brevotoxin (e.g. Red Tide). Researchers show that cetaceans use several strategies for success in this race. They have developed tools to help wildlife managers and health professionals assess disease risk from the perspective of how individual animals are engineered to recognize the molecules of microorganisms in the environment and launch an immune response.
Polar bears gorged on whales to survive past warm periods; won't suffice as climate warms - A new study found that while dead whales are valuable sources of fat and protein for some polar bears, this resource will likely not be enough to sustain most bear populations in the future when the Arctic becomes ice-free in summers.
PCB pollution threatens to wipe out killer whales - A new study shows that more than 40 years after the first initiatives were taken to ban the use of PCBs, the chemical pollutants remain a deadly threat to animals at the top of the food chain
Aerial survey reveals great diversity and abundance in NE Canyons Marine National Monument - Airborne marine biologists were amazed by the sheer abundance and diversity of large marine wildlife in their recent aerial survey of the Northeast Canyons and Seamounts Marine National Monument, the only marine national monument on the East Coast, about 150 southeast of Cape Cod.