The United States population of California Sea Lions (Zalophus californianus) range from southeast Alaska to the Pacific coast of central Mexico. While this population does not breed in Canada, some sub-adult and adult males migrate northwards to British Columbia (BC) during the non-breeding season with an arrival in August–October and a departure in April–May. The population in coastal BC was assessed in 1985 and again in 2023 from dedicated over-winter aerial surveys. The most recent assessment used counts from 2020–2021surveys that were restricted to southern BC as few animals have been documented further north.

Additional observations of California Sea Lions were collected while surveying sites for Steller Sea Lions. These opportunistic counts increased from approximately 1,000 animals in the mid-2000s to several thousand individuals in more recent years. Historically occupied sea lion rookeries and haul-out sites were surveyed with nearby areas monitored for potential shifts in distribution. This dataset contains counts that have been collected from sightings of individuals from 1971 through 2021and replaces a previous dataset limited to the 2016/2017 survey season.