WASHINGTON – The government on Monday recommended a speed limit for commercial ships along the Atlantic coast where collisions with the endangered right whale threaten its existence.

About 300-400 of the whales are left in the wild, and they migrate annually between their southeastern Atlantic breeding grounds to feeding areas off the Massachusetts coast, intersecting busy shipping lanes.

The head of the National Oceanic and Atmospheric Administration said Monday the new limit, the first to be instituted on the East Coast for a marine creature, was needed to assure its survival. The rule would set a speed limit of 11.5 mph (10 knots) within 23 miles (20 nautical miles) of major mid-Atlantic ports and throughout the whale’s breeding and feeding areas. The new regulation would cover ships 65 feet or longer and expire in five years if not renewed. Boats from federal agencies would be exempt.

“The bottom line is that this critically endangered species needs our help,” said retired Navy Vice Admiral Conrad C. Lautenbacher, the agency’s administrator.

But the latest version of the ship strike regulation differs from a draft released more than a year ago that was delayed in part because of objections from Vice President Dick Cheney’s office and White House economists over the accuracy of the science linking ship speed to whale deaths.

“NOAA’s decision on these measures is based on the best data and scientific understanding available,” White House environmental adviser James L. Connaughton said Monday.

The option selected on Monday and released with an 850-page analysis of its environmental and economic impacts is narrower than the 34-mile-wide coastal speed zone first proposed for the mid-Atlantic coast by marine scientists in June 2006. Last year, in response to questions from the White House, agency experts said moving the speed-limit zone closer to shore in that region would be less protective of right whales.

On Monday, agency officials said the reduced area still covered 83 percent of all right whale sightings.

Environmentalists said the changes were the latest to come from an administration that has consistently bucked scientific research.

“What we have seen over and over again where economics and partisanship and political interests bump up against the science, science loses,” said Francesca Grifo, director of the Union of Concerned Scientists’ Scientific Integrity Project.

The analysis published Monday said the lower speed limit could cost ferry operators $8.6 million in lost revenues annually and even have an effect on the whale watching industry, which is expected to lose $1.3 million under the proposed regulation.

North Atlantic right whales have been protected by endangered species laws since 1970, yet despite warning systems around heavily traveled ports, aerial surveys to map whales in shipping lanes, and improvements in fishing gear, their population has yet to recover.