Migrating blue, fin and humpback whales are frequently hit by ships in California’s coastal waters, where they are lured by the region’s plentiful krill.
The slow-moving and endangered marine mammals are highly vulnerable to ship strikes, since many of their feeding and migration areas overlap with shipping lanes.
Five whales were killed by ship impacts off San Francisco alone in 2010.
The International Maritime Organization has now approved vessel lane changes that will go into effect this year on approaches to San Francisco Bay and the ports of Los Angeles and Long Beach, as well as in the Santa Barbara Channel.
“This is a win-win situation” for maritime safety and whale protection, William Douros of the National Oceanic and Atmospheric Administration's Office of National Marine Sanctuaries said in a statement.
A 2007 shift in shipping lanes off Massachusetts reduced the risk of ships striking whales by 81 percent.