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Friday, October 1, 2010

Endangered Freshwater River Dolphins

Indus river dolphin
freshwater-dolphins-threatened-indus-river Local men rescue an Indus river dolphin in Sind Province, Pakistan.

The endangered Indus dolphin is the only river dolphin species on the rise, with populations estimated at around 1,700 in 2006, up from 1,200 in 2001.

Bolivian river dolphin
freshwater-dolphins-threatened-bolivian-river This baby Bolivian dolphin was rescued in the summer of 2010 in the Pailas River, a tributary of the Rio Grande, when drought led to lower-than-usual water levels.

The Bolivian river dolphin comes equipped with a flexible body that allows it to make its way through the tree roots of flooded forests.

All three South American river dolphin species compete for habitat with fishers who sometimes use the dolphin as bait, according to WWF. But, the new report goes on to state that the primary threat to the Bolivian dolphin is mercury pollution from small-scale gold mines.

 Tucuxi River Dolphin
freshwater-dolphins-threatened-tucuxi A dorsal fin skims the surface of the Yavari River in Peru.

Tucuxi look like bottlenose dolphins but have longer noses and broader flippers. The species is found throughout the Amazon region, with the exception of Bolivia.

Both Tucuxi and Irrawaddy dolphins are distinct from the other five species in that they are part of the Delphinidae family of mostly ocean-dwelling dolphins. Both species have marine populations, as well as freshwater populations.

Ganges River Dolphin
freshwater-dolphins-threatened-ganges-river A Ganges river dolphin, or Susu as it is known locally, waits at the surface of the Karnaphuli River in Bangladesh, where it comes up to breath every minute or so. WWF estimates that there are fewer than 2,000 of the endangered species left in the river system made up of the Ganges, Brahmaputra, Meghna, and Karnali Rivers in Bangladesh, India, and Nepal.

In 2009, India declared the Ganges river dolphin the national aquatic animal, a huge step toward conservation, said Ravi Singh, CEO of WWF India.

Irrawaddy River Dolphin
freshwater-dolphins-threatened-irrawaddy An Irrawaddy dolphin breaches the Mekong River in Cambodia. According to WWF, fishers in Myanmar's Irrawaddy River work in cooperation with Irrawaddy dolphins. The dolphins herd fish along side boats as they feed. The Irrawaddy dolphin's range has been limited to a 120-mile (190-kilometer) stretch of the Mekong, and small sections of the Irrawaddy and Mahakam Rivers, each subpopulation reduced to the critically endangered number of less than 75.

Ninety-two animals, more than half of them calves, died in fishing nets between 2003 and 2009 on the Mekong, according to WWF.

Amazon river dolphin
01-tracking-dolphin-615Tracking prey deep in the forest, freshwater dolphins make the most of the Amazon’s prodigious annual flood.

Legends around river dolphins abound. Amazon river dolphins are said to be shape shifters, changing into handsome men at night.

Often known as pink dolphins or "boto," Amazon river dolphins face the same risks as the other two South American species, including the habitat fragmentation that comes with dam building along the Amazon and its tributaries.

The species is widely distributed along the Orinoco and Amazon River Basins, in Venezuela, Colombia, Ecuador, Peru, Brazil, Suriname, and Guyana.

Yangtze River Dolphin
aquatic-vwhite-dolphin-chinaThe Yangtze River’s white fin dolphin, or baiji, in China, was believed to be extinct until 2007—when evidence turned up via amateur video that the species still survived.

Scientists say the mammals plied Chinese rivers for more than 19 million years before humans radically altered their habitat by overfishing, heavy freight traffic, and pollution. If any dolphins can be found, a captive breeding program might represent the last, slim chance to save the species.

Yangzte Finless Porpoise
freshwater-dolphins-threatened-yangtze-finless-porpoiseThe Yangtze finless porpoise is one of two large marine mammals that used to ply China's longest river.

Just 1,600 to 1,800 of the finless porpoises were counted in 2006 along the middle Yangtze and in two lakes. A population of the porpoise that has been protected in one of the Yangtze's oxbow lakes—remnants of where the river used to run—has grown by three or four calves a year.

To help the animals, local governments open sluice gates at 40 lakes along the Yangtze, returning, to some degree, the seasonal flow of the river and the dolphin to a larger stretch of its original habitat, said Lifeng Li, director of freshwater programs at WWF.

River dolphins, many elusive, are the canaries in the coal mine of the planet’s freshwater ecosystems, according to WWF. The threats facing dolphins are the same threats facing people, the environmental nonprofit's new report states.

“Unsustainable fishing practices both harm dolphins and erode the basis of fishermen’s livelihoods; toxic chemicals used in agriculture and mining affect the health of people and dolphins alike; and loss of natural river flows and habitats decreases the productivity of the freshwater ecosystems that sustain both human societies and river dolphins.”

source: National Geographic

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