For hundreds of endangered whales that could be accidentally struck by ships heading to and from the ports of Long Beach and Los Angeles, one mile could mean the difference between life and death.

Next year, shipping lanes that intersect three national marine sanctuaries off the California coast will be moved to help curb encounters between whales and ships, after the International Maritime Organization recently adopted changes to the routes. | » Pacific gray whale migration begins

"It's a big deal when you're rerouting ships; imagine moving the 405," said Sean Hastings, resource protection coordinator for the National Oceanic and Atmospheric Administration's Channel Islands National Marine Sanctuary. "You can't move the animals out of the way of traffic, so we found a way to slightly adjust the traffic, and that will definitely add a buffer to the whales."

Ships approaching the San Francisco Bay, the Santa Barbara Channel and the ports of Los Angeles and Long Beach often travel through NOAA's Cordell Bank, Gulf of the Farallones and Channel Islands national marine sanctuaries where blue, humpback and fin whales gather and eat.

This has led to whale deaths. Four blue whales were killed "by confirmed or likely" ship strikes in and around the Santa Barbara Channel in 2007, while two blue, one humpback and two fin whales were killed in the San Francisco area and along the north-central California coast in 2010.

Every year, about 200 blue whales go to the Santa Barbara Channel and spend four to six months feeding on krill, which is often found beneath the shipping lanes. The migrating whales are a popular sight for Southern California tourists as well, and the unofficial start of whale watching season kicked off this week.

"We have one of the largest concentrations of blue whales," Hastings said, adding that it represents more than 10 percent of the North Pacific Ocean population of blue whales. "Their numbers are a fraction of what they used to be historically."

To help create a separation between whales and ships, NOAA and the Coast Guard worked for two years to adjust the traffic separation scheme, which is a kind of freeway system for ships.

"The collaboration between NOAA and the Coast Guard in reviewing and modifying these vessel traffic separation schemes demonstrates the strong working relationship between our two agencies," Rear Adm. Karl Schultz, 11th Coast Guard district commander, said in a statement. "The modifications to the traffic lanes balance the safe and efficient flow of commerce within and between our nation's ports, with NOAA's goal of reducing whale strikes from vessels."

The two-mile space on the water buffering the northbound and southbound shipping lanes will shrink down to one mile, and the outside lane will shift one mile north toward the mainland.

"By shifting these lanes ... we're moving them away from the feeding grounds of endangered blue, fin and humpback whales," Hastings said.

The move is similar to an effort in 2007 by NOAA's Office of National Marine Sanctuaries to shift shipping lanes in Stellwagen Bank National Marine Sanctuary, off the coast of Massachusetts. The risk of ships striking whales has been reduced by 81 percent as a result of the traffic adjustment, according to the NOAA.

Hastings said the one-mile buffer is more than adequate for navigational safety. The two-mile buffer was designed in the 1980s when ships weren't easily aware of each other, but technology has helped ships keep better track of their movement.

Regina Asmutis-Silvia, executive director of Whale and Dolphin Conservation's North American office, applauded the traffic move.

"This is a really important step to being able to reduce the threat of vessel strikes to whales," she said.

karen.robes@presstelegram.com, 562-714-2088, twitter.com/KarenMeeksPT