Groups of California's famed sea lions started appearing on a dock next to Pier 39 in January 1990. They grew from about 50 at that time to more than 1,700 last year.
There were 250-300 sea lions at Pier 39 Friday, a number that will only grow as San Francisco heads into summer.
That is good news for tourist merchants, who have turned this annual return of the sea lions into a marketing opportunity.
"When they're gone they are missed very much," Bob Partrite of the Pier Market restaurant said. "People ask, 'Where they are? Where did they go?'"
The sea lions travel up and down the coast searching for food and places to rest, according to the Marine Mammal Center.
The California sea lion is not an endangered species, but, as the Marine Mammal Center points out, it is what they call an indicator, because it is at the top of the food chain. As sea lions go, so goes the health of the Pacific Ocean and San Francisco Bay.