SHEDIAC, N.B. -- As Canadian officials scramble to determine whether an endangered whale caught in fishing rope off Quebec's Gaspe Peninsula may have freed itself, federal Fisheries and Oceans Minister Dominic LeBlanc is promising a new set of rules around commercial fishing gear to protect the large marine mammals.

A North Atlantic right whale was spotted entangled in ropes during a fly-over of the Gulf of St. Lawrence Monday, but LeBlanc said aerial and water patrols were unable to locate it Tuesday.

"We identified a pod of 13 other North Atlantic right whales that were in the exact vicinity of where the other whale had been spotted entangled the previous day," he said. "We're continuing to patrol the area but scientists believe it's possible that perhaps the whale freed itself."

Officials are investigating whether the fishing gear rope that entangled the whale was in the area legally or had been lost or abandoned, which LeBlanc said has been the case with other entanglements this summer.

He said the rope may have been fishing gear for the herring fisheries or abandoned crab traps, and that the department is investigating and may press charges.

Ten right whales have died since June in the Gulf of Saint Lawrence, an unprecedented number of deaths for the endangered marine mammal.

With an estimated population of 500 around the world, conservation groups and marine scientists have warned the North Atlantic right whale is at imminent risk of extinction.

The biggest threats to the whales appear to be ship strikes and fishing gear entanglements.

LeBlanc said the federal government will usher in a new set of rules around fishing gear to improve the safety of whale migration in the Gulf of St. Lawrence.

"Next year's season of potential whale migration will have a different set of rules around fishing gear, fishing practices, fishing equipment and probably the question of marine transportation as well in Canadian waters," he said.

Ottawa already ordered large vessels to slow down in the Gulf earlier this month, in an effort to reduce the frequency and severity of ship strikes as it probes the deaths.

Vessels of 20 metres or more are required to slow to 10 knots -- or about 19 kilometres per hour -- while travelling in the western Gulf, from the Quebec north shore to just north of Prince Edward Island.

Coast Guard officials are also patrolling the area in an effort to keep tabs on the whales.

"If the weather and the daylight hours allow, we have eyes on the Gulf from the air and we have eyes on the Gulf from the water," he said. "It's hard to imagine we could deploy more assets."

The whales, which summer off New England and Atlantic Canada, are among the most imperilled marine mammals on Earth. Populations have only slightly rebounded from the whaling era, when the blubber-rich baleen whale became nearly extinct.

While 10 of the whales have died in Canadian waters, three have been found dead in U.S. waters. In all, 13 of the marine mammals have been found dead this year, more than triple the annual average of 3.8 in Canada and the U.S.

The alarming number of deaths has prompted the United States government to launch an investigation.

The U.S. National Oceanic and Atmospheric Administration's Fisheries branch declared the deaths "an unusual mortality event," triggering a sweeping study into the cause of the deaths, including environmental and habitat conditions, threats from commercial fishing and shipping and other risk factors.

NOAA Fisheries officials will work with counterparts at Fisheries and Oceans Canada on sampling and data collection, analysis and recommendations for future responses.

Last month, lobster fisherman Joe Howlett was killed in waters off eastern New Brunswick after he freed a right whale caught in fishing gear.

The death prompted LeBlanc to order a stop to disentangling right whales, and on Wednesday he said he's not prepared to authorized whale disentanglements until a report into Howlett's death is complete.

"Until we have the benefit of a Transport Canada inquiry, I cannot in good conscience authorize our personnel or others to approach North Atlantic right whales on the same vessel and in similar circumstances," he said. "We're assessing what other options might be available but it won't be a similar vessel and it won't be a similar procedure."

By Brett Bundale in Halifax