Scientists fear rare dolphin driven to extinction by human activities

Sep 11, 2007

An international research team, including biologists from NOAA Fisheries Service, has reported in an online scientific journal that it had failed to find a single Yangtze River dolphin, or baiji, during a six-week survey in China. The scientists fear the marine mammal is now extinct due to fishing and commercial development, which would make it the first cetacean to vanish as result of human activity.

The research paper, published last month in the online journal Biology Letters, reports that an intensive acoustical and visual survey of the main Yangtze River where the baiji live failed to find what was already considered to be one of the world’s most endangered species.

“The last time these animals were surveyed was in the 1990s when only 13 were found,” said Barbara Taylor, a marine biologist at NOAA’s Southwest Fisheries Science Center in La Jolla, Calif., and one of the researchers on the scientific team that was working with local scientists at the invitation of the Chinese government. “This time, we detected no baiji, either visually or acoustically. This would be the first human-caused extinction of a dolphin or whale and it is particularly sad for the last member of a family of a species that is over 20 million years old.”

The baiji is one of only a few dolphin species that is known to have adapted from the ocean to a freshwater environment. The likely cause of the baiji’s decline is from the use of fishing nets with hooks that snag and drown the dolphins as bycatch. Other causes may include habitat degradation.

Scientists are also concerned that this could just be the first of many human-caused extinctions of marine mammals that are under stress around the world.

“We are concerned about several vulnerable species of dolphin and porpoise around the world, including the vaquita," said Nicole Le Boeuf, international fisheries biologist for NOAA Fisheries. The vaquita is a critically endangered porpoise found only in the uppermost part of Mexico's Gulf of California. Vaquita have been reduced to only a few hundred animals because of accidental deaths in small-scale fishing nets. In addition to the vaquita, many coastal dolphins and porpoises in other parts of the world are highly vulnerable to being accidentally caught in similar fishing gear.

“The vaquita and other highly imperiled marine mammals represent a major conservation challenge,” said Le Boeuf. “There is very real global concern for these species, especially with the all but certain loss of the bajii in China. NOAA and its international partners are working together to lend their support to Mexico and other nations with similar species in their coastal and inland waters."

In the end, it may come down to conserving not just dolphins and porpoises, but local communities as well. "We have to find a way to let local fishermen put food on their tables that doesn't involve putting nets in the water that decimate these coastal dolphin species," said Taylor.

Source: NOAA National Marine Fisheries Service

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