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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

Proactive conservation of New Zealand blue whales - Researchers have developed a method for forecasting the locations where a distinct population of New Zealand blue whales are most likely to occur up to three weeks in advance.
‘Whoop’ – new autonomous method precisely detects endangered whale vocalizations - One of the frequently used methods to monitor endangered whales is called passive acoustics technology, which doesn't always perform well. In the increasingly noisy ocean, current methods can mistake other sounds for whale calls. This high 'false positive' rate hampers scientific research and hinders conservation efforts. Researchers used artificial intelligence and machine learning methods to develop a new and much more accurate method of detecting Right whale up-calls -- a short 'whoop' sound that lasts about two seconds.
Warming Atlantic drives right whales towards extinction - Warming oceans have driven the critically endangered North Atlantic right whale population from its traditional and protected habitat, exposing the animals to more lethal ship strikes, disastrous commercial fishing entanglements and greatly reduced calving rates. Without improving its management, the right whale populations will decline and potentially become extinct in the coming decades, according to a recent report.
Study shows a whale of a difference between songs of birds and humpbacks - These findings challenge the results of past studies that vocal variations in humpback whale songs provide information about a singer's reproductive fitness. Instead, the morphing appears to reveal the precise locations and movements of singers from long distances and may enhance the effectiveness of song parts as sonar signals.
Development and evolution of dolphin, whale blowholes - New research is shedding light on how the nasal passage of dolphins and whales shifts during embryonic development from emerging at the tip of the snout to emerging at the top of the head as a blowhole. The findings are an integrative model for this developmental transition for cetaceans.