After avoiding B.C.'s coast for decades, blue whales are returning to our waters to feed in the areas where they were once hunted to near extinction.Scientists hoped the recent sightings meant an increase in the population of the highly endangered whales, but an article to be published this month by the U.S. Marine Mammal Science journal suggests the whales have migrated north from California, following the tiny shrimp on which they feed.It's a pattern the massive whales might have followed for decades, chasing krill that move with the 20 or 30-year cycle of cool ocean water."It's good news to see these whales back in our waters," said John Ford, co-author of the article and a whale researcher with the federal fisheries and oceans department."It's encouraging that the whales are out there using this habitat. Now we have to find out what areas are important to them and then try to protect them."Accidental collisions with ships pose the biggest threat to blue whales, he said.In August 2007, Ford was part of survey team that spotted five blue whales off the Queen Charlotte Islands. Researchers believe about 2,000 of the sleek, steel-grey whales live off the west coast, between Alaska and Mexico. Worldwide, there are only about 10,000 blue whales.