Yangtze river dolphin driven to
extinction
· Intensive survey reveals disappearance of species
· Scientists blame shipping, hunting and fishing
The Yangtze river dolphin, until recently one of the most
endangered species on the planet, has been declared officially
extinct following an intensive survey of its natural habitat.
The freshwater marine mammal, which could grow to eight feet long
and weigh up to a quarter of a tonne, is the first large vertebrate
forced to extinction by human activity in 50 years, and only the
fourth time an entire evolutionary line of mammals has vanished
from the face of the Earth since the year 1500.
Conservationists described the extinction as a "shocking tragedy"
yesterday, caused not by active persecution but accidentally and
carelessly through a combination of factors including unsustainable
fishing and mass shipping.
In the 1950s, the Yangtze river and neighbouring watercourses had a
population of thousands of freshwater dolphins, also known as
Baiji, but their numbers have declined dramatically since China
industrialised and transformed the Yangtze into a crowded artery of
mass shipping, fishing and power generation. A survey in 1999
estimated the population of river dolphins was close to just 13
animals.
Historically, the species had been revered and achieved nearly
demi-god status among fishermen who recounted tales of dolphins
being reincarnations of drowned princesses. But in Mao's Great Leap
Forward, the overthrowing of idols saw their protection lifted and
they were hunted for food and their skin.
Sam Turvey, a conservation biologist at London Zoo, worked with
Chinese government scientists to survey the entire 1,669km stretch
of the Yangtze river downstream of the giant Three Gorges Dam to
Shanghai, a region which has been the natural habitat for river
dolphins.
The team scoured the river four times in two boats during the
six-week survey, using high-powered binoculars to spot the
dolphins. Sensitive hydrophones were towed behind to listen for
their calls.
The researchers hoped that if any dolphins were spotted, they could
be taken to a reserve in an oxbow lake which was once part of the
Yangtze in the hope of boosting their numbers. But at the end of
the survey, they had neither seen nor heard any sign of the
dolphins, according to their report in the journal Biology
Letters.
"We passed through what were supposed to be Baiji hotspots and
every day there was nothing. The hopes of each person on the survey
died at different points; everyone had a moment of realisation that
we weren't going to find anything," said Dr Turvey.
Around half of all river dolphins were killed as a result of
indiscriminate and often illegal fishing practices. Though banned
for the past 30 years, some ships still drag long lines of unbaited
hooks. "They just drift through the water snagging everything. They
slash and entangle and suffocate the dolphins," said Dr Turvey. Low
employment in the 1980s and 1990s saw a rise in unskilled
fishing.
Dr Turvey said conservation organisations had been quick to call
for action to protect the river dolphin, but many were too cautious
to take meaningful action.
"The loss of such a unique and charismatic species is a shocking
tragedy. The Yangtze river dolphin was a remarkable mammal that
separated from all other species over 20m years ago. This
extinction represents the disappearance of a complete branch of the
evolutionary tree of life," Dr Turvey added.
(source:
The Guardian)
