June 29, 2010
Finless Porpoises Becoming More Endangered
Finless porpoises may be more endangered than previously thought.
A new study of finless porpoises, a rare type of toothed whale, found that there are two species, not one, and they rarely intermingle.
The whales inhabit a wide range of tropical and temperate waters around the Indo-Pacific region.
Zoologists noted for a long time that these porpoises appear to differ depending on where they live.
Those living around China have different morphological characteristics depending whether they live in the Yellow Sea, South China Sea or up the Yangtze river, which holds fresh rather than seawater.
However, a new study published in the journal Marine Biology has revealed just how distinct each population of finless porpoise is.
"The most surprising finding of this study is that the Yangtze finless porpoise represents a distinct genetic grouping, which is distinct from marine porpoises," Professor Guang Yang of Nanjing Normal University in China, who conducted the study with Professor Michael Bruford of Cardiff University, UK and colleagues at Nanjing, told BBC news.
Conservationists consider all finless porpoises to be the same species.
However, Yang and Bruford's team analyzed the genes of 125 finless dolphins living around China, including in the Yellow and South China Sea and Yangtze river.
They said that the results suggest that special regard should be given to the freshwater porpoises, which should be managed and conserved separately.
"The freshwater nature of this population makes it unique," says Prof Yang.
The scientists say that the "jury is still out" on whether the Yangtze finless porpoise should be granted species status, as more data is required.
However, it is so genetically unique that special efforts should be made immediately to protect it.
"The most recent field survey conducted in 2006 suggested that there were around 1,000 individuals in the Yangtze River," Yang told BBC.
"This is much smaller than previous estimates, suggesting a significant population decline in the past two decades."
China is already considering upgrading the conservation status of the Yangtze population of finless porpoises.
However, "at least in China, most conservation biologists and cetologists have a strong feeling that the Yangtze finless porpoise has a very high risk of extinction, and is very likely to follow the Baiji to extinction within a short-term period unless conservation measures are put in place," Yang told BBC.
The Yangtze River holds the dubious distinction of being the site of the first recorded extinction of a cetacean since records began.
Conservationists declared the Baiji extinct in 2007, which is a species of river dolphin endemic to the Yangtze River, after repeated surveys over many years failed to sight a single animal.
Development, industry, pollution, overfishing and the commercial use of the river by boats have all been blamed for contributing to the Baiji's demise.
The scientists' survey also revealed that finless porpoises living in the sea should be considered two separate species.
Porpoises living in the Yellow Sea are distinct from those in the South China Sea.
The genetic data showed there is very little or no gene flow between these two species, even in areas where they overlap.
The scientists say that each marine population should be conserved separately.
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