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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

Technique allows dolphin pregnancy exams to mirror those in humans - In a groundbreaking study, scientists have developed a new ultrasound technique for evaluating dolphin fetuses at all stages of gestation.
A 'pivotal' moment for understanding whale evolution - We could be getting closer to understanding how feeding behaviors in whales and dolphins have evolved over time.
Consider marine life when implementing offshore renewable power - With countries adopting green energy practices, renewable energy now accounts for a third of the world's power. As this trend continues, more countries are looking to offshore energy sources to produce this renewable energy. Researchers identify situations where green technology such as wind turbines, wave energy converters, and other marine renewable energy devices (MREDs) have had negative consequences on marine life.
Resident orcas' appetite likely reason for decline of big Chinook salmon - Large, old Chinook salmon have mostly disappeared from the West Coast. A new study points to the recent rise of resident killer whales, and their insatiable appetite for large Chinook salmon, as the main driver behind the decline of the big fish.
The limits of ocean heavyweights: Prey curb whales' gigantic size - Scientists collected data from hundreds of feeding whales, allowing them to determine how much energy species of different sizes invest to capture their prey and which of these species reap the greatest rewards for their efforts. Their findings reveal that body size in all whales is limited by the availability of their prey, but only filter-feeding whales have evolved a feeding strategy that drives them to achieve the largest body sizes to have ever evolved.