Some bits from the article, my emphasis in bold:

It is the first large animal to be wiped from the planet for 50 years, and only the fourth entire mammal family to disappear in 500 years. And it was driven to its death by mankind...

By Jeremy Laurance
Published: 08 August 2007

After more than 20 million years on the planet, the Yangtze river dolphin is today officially declared extinct, the first species of cetacean (whale, dolphin or porpoise) to be driven from this planet by human activity.

To blame for its demise is the increasing number of container ships that use the Yangtze, as well as the fishermen whose nets became an inadvertent hazard.

This is no ordinary extinction of the kind that occurs frequently in a world of millions of still-evolving species. The Yangtze freshwater dolphin was a remarkable creature that separated from all other species so many millions of years ago, and had become so distinct, that it qualified as a mammal family in its own right. It is the first large vertebrate to have become extinct for 50 years and only the fourth entire mammal family to disappear since the time of Columbus, when Europeans began their colonisation of the world.



Sam Turvey, conservation biologist at the Zoological Society of London, who led the expedition to find the Yangtze dolphin and is chief author of the paper, said: "The loss of such a unique and charismatic species is a shocking tragedy. This extinction represents the disappearance of a complete branch of the evolutionary tree of life and emphasises we have yet to take full responsibility in our role as guardians of the planet."

The cause of the freshwater dolphin's demise was instead all too plain to the investigators. It had become a victim of the world's most populous country's race to get richer. One tenth of the world's population live in the Yangtze river basin. During the expedition, scientists counted 19,830 ships on the 1,669km of the river they surveyed - one large freight vessel every 800m.

The Yangtze dolphin navigated by sonar - its eyes are useless in the murky water - but in a motorway jammed with container ships, coal barges and speed boats, its sonar was deafened and it ran a high risk of being hit or torn by propellers.

An even greater threat came from the nets and 1,000m lines of hooks used by fishermen.

Although they did not intend to catch dolphins, the creatures became entangled in the nets or lacerated by the bare hooks - almost half of all dead baiji found in the past few decades have died in this way. In addition, pollution had fouled their natural habitat and completion of the Three Gorges Dam worsened the decline in smaller fish on which the baiji fed.