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

New new genus and species of extinct baleen whale identified - Paleontologists are rewriting the history of New Zealand's ancient whales by describing a previously unknown genus of baleen whale, alive more than 27.5 million years ago and found in the Hakataramea Valley, South Canterbury.
Diving deep into the blue whale genome reveals the animals’ extraordinary evolutionary history - For the first time, scientists have deciphered the complete genome of the blue whale and three other rorquals. These insights now allow tracking the evolutionary history of the worlds’ largest animal and its relatives in unprecedented detail. Surprisingly, the genomes show that rorquals have been hybridizing during their evolutionary history. In addition, rorquals seem to have separated into different species in the absence of geographical barriers. This phenomenon, called sympatric speciation, is very rare in animals.
Like human societies, whales value culture and family ties - In a detailed genetic kinship study, an international team is the first to reveal that just like human societies, beluga whales appear to value culture and their ancestral roots and family ties. They have demonstrated that related whales returned to the same locations year after year, and decade after decade. Not only do these whales know where to go and where not to go, they are passing on this information from one generation to the next.
Bowhead whales, the 'jazz musicians' of the Arctic, sing many different songs - Four winters of audio recordings of bowhead whales singing under the ice off Greenland show a surprise variety in this animal's repertoire. Bowhead whales' vocalization patterns are very different from the only other whale known to make distinct songs, the humpback.
Dolphins tear up nets as fish numbers fall - Fishing nets suffer six times more damage when dolphins are around - and overfishing is forcing dolphins and fishermen ever closer together, new research shows.