Tens of thousands of dolphins, porpoises and other small whales were unnecessarily killed by U.S. fishermen last year, but that number is only a fraction of the half million slaughtered worldwide, according to estimates published recently by the Environmental Investigation Agency (EIA).

The London-based conservation group, which previously focused on the plight of endangered elephants, said the figure could be much higher if undocumented slaughters could be tallied. It added that many species of small cetaceans, the branch of the whale family that includes these marine mammals, are being pushed to the brink of extinction.

Slaughter figures, published in a report on a country-by-country basis, are being presented to the International Whaling Commission (IWC) at its annual meeting this week in the Netherlands. The report calls on members to implement regulations to protect the marine mammals worldwide.

"Small cetaceans need protection, and when that protection isn't forthcoming at the national level, the global community through forums like IWC needs to step forward and take action," said Clifton Curtis, an ocean expert with the environmental group Friends of the Earth. "Practice in other developing and developed nations shows a barbaric disregard for marine mammals."

The tuna industry has been the biggest culprit, killing hundreds of thousands of the small cetaceans, which get caught in drift nets, any one of which can extend in the open water for 40 miles. The trapped mammals, which must surface to breathe, either drown or are killed by fishermen.

In Japan last year, where at least 50,000 small cetaceans were killed in coastal waters and tens of thousands more in offshore fisheries, dolphins are also being killed for food. Their meat is often sold on the market as whale, environmental groups say.

Regional populations of Dall's porpoise and striped dolphin have been reduced to such low levels that EIA believes they could be extinct by the turn of the century if the slaughtering is not curtailed.

"It's a global disgrace that certain countries are being allowed systematically to wipe out the world's friendliest and most intelligent creatures," said Tina Harper, a director for EIA's U.S. office. "In addition to the horrifying numbers killed, the methods by which they are slaughtered are extremely cruel, causing the dolphins an agonizing death."

EIA is calling on the United States, Britain, Australia and other members of the IWC to support the implementation of regulations on killing small cetaceans, but Japan and other countries such as Mexico, which killed an estimated 40,000 dolphins last year, are expected to oppose regulations. In addition, non-member countries such as Taiwan and Peru, which kill tens of thousands of marine mammals yearly, would not be subject to IWC regulations.

"We hope that this report will alert the public to bring pressure to these non-member countries to take immediate action to protect their dolphin populations," Harper said. "It's too bad that these animals have to become endangered before measures are taken to protect them."