Past commercial whaling of Blue Whales is the main factor responsible for the population decline. Throughout the North Pacific between 1910 and 1965, commercial whalers harvested at least 9,500 Blue Whales, some of which were caught by shore-based whaling stations in British Columbia from the early 1900s to 1965. Since the end of commercial whaling, human threats have included collisions with ships, increasing whale-watching activity, entanglement in fishing gear, and pollution (especially oil pollution).