A proposed rule that would impose ship speed limits in North Atlantic right whale habitat is being challenged by the shipping industry and blocked by the White House.

The rule would restrict ship speeds to 10 knots for most ships 20 meters or longer during key whale migration periods. The speed limit would have no affect on lobster boats, and military vessels would be exempt. In the Bay of Fundy, the speed limit would only apply intermittingly in areas where right whales are spotted.

The final speed limit ruling is the culmination of eight years of negotiations and lawsuits between conservationists and the National Marine Fisheries Service (NMFS). NMFS lawyers agreed to come out with a final ruling on ship speed limits during a lawsuit earlier this year, and officials announced the speed limit in June. Conservationists have long contended that ship strikes are the second-leading cause of death for critically-endangered right whales, resulting in at least seven of the 18 known fatalities in 2006 and most likely a factor in several other deaths where the cause of death was not determined.

“2005 and 2006 were really killer years in terms of right whale strikes,” said Vicki Cornish, director of marine wildlife conservation for the Ocean Conservancy.

Cornish has hoped a ship speed limit, alongside new shipping lanes and lobster trap rope regulations, would help stop the decline in numbers of the 350 remaining North Atlantic right whales

“Having [the three of them] hopefully will go a long way,” Cornish said.

But in an unusual move, the White House Council of Economic Advisors has stalled the measure while it conducts an independent review of the science behind the speed limit rule. The council took action shortly after the Office of Management and Budget (OMB) received a letter critical of ship speed limits from the World Shipping Council, a trade organization representing major international shipping lines. Conservationists suggest the timing is not a coincidence.

It’s common for OMB to review new rules for economic impact, but it’s unprecedented for the office to weigh in on scientific matters. It’s unclear what level of scientific expertise the office could possibly have, said Amy Knowlton, research scientist for the New England Aquarium.

“They’re sort of overstepping their bounds,” Knowlton said.

Cornish, once an employee for the NMFS, said that while the move is like nothing she remembers, it’s consistent with actions by the White House in recent years.

“This administration has weighed in on these issues more than any other administration,” she said.

In its letter to OMB, the shipping council argued against speed limits largely on scientific grounds. Using research findings from ship strike studies, the council argued the speed limit is, at best, arbitrary, and may do more harm than good. A speed limit of 10 knots might actually put whales at greater risk, the letter stated, because large ships would have less maneuverability to avoid collisions.

“There is virtually no evidence to indicate a correlation between vessel speed and the severity of injury in the event of a collision,” the council letter stated.

The letter said the majority of known ship strikes involve ships 20 meters long or less or military vessels; therefore, any speed limit that exempts those vessels would be ineffective. Imposing speed limits on large shipping vessels would impose undue economic hardship for little gain, the letter argued.

But the authors of one of the studies cited in the letter, oceanographers C.T. Taggart and A.S.M Vanderlaan of Dalhousie University in Halifax, say the shipping council has misinterpreted the study’s findings. Reduced ship speeds do reduce the severity of impact with a whale at any speed other than 4 to 6 knots, their research shows; it’s simply a matter of physics.

“When the vessel is much more massive than the whale…it is only the mass of the large whale…and the speed of the vessel that determines the impact forces involved in the collision and the severity of injury to the whale,” they wrote in a letter to the OMB.

Documented ship strikes generally involve smaller ships because captains of those ships are more aware that a strike has occurred, argued Knowlton in her own letter to the OMB. In some cases, the strike disables the vessel.

Most ship strikes go unreported. In one of the only known ship strikes involving a large vessel, observers on board saw the strike occur but didn’t feel the strike.

“Captains of huge ships, such as container ships, tanker, and cruiser ships may not be aware of a collision with a whale has occurred and thus do not report the incident,” Knowlton quoted a 2003 ship strike study as saying in her letter to the OMB.

Knowlton believes the shipping council is going by an incorrect assumption that whales are passive in the event of a possible collision and do not make an attempt to get out of the way. In her experience on whale research cruises in Lubec, she’s discovered otherwise.

“We’ve had the whales respond quite often to our vessels,” she said in a telephone interview.

A ship speed limit would buy whales time to maneuver out of harm’s way, she said.

The OMB has already missed two deadlines for delivering a final ruling on the proposed speed limit. A handful of congressional members from the House and Senate, including Maine Rep. Tom Allen and Sen. Susan Collins, have sent letters to the White House urging the Bush Administration to adopt the speed limit without further delay.

But if the administration continues to stall and the speed limit remains in limbo, conservationists fear they’ll have little legal recourse to save the rule. Cornish said conservationists have already exhausted their legal options in previous lawsuits to get to this point.

“We’re grasping for straws,” Cornish said. “We really are at rope’s end to protect these whales.”