These boisterous barking sea lions started arriving in droves, taking over area docks in January 1990 shortly after the 1989 Loma Prieta earthquake. At first they numbered from 10-50, but due to a plentiful herring supply, available dock space and the marina’s protected environment, the population grew to more than 300 within a few months. Each winter, the population can increase up to 900 sea lions, most of which are male. During the summer months, the sea lions migrate south to the Channel Islands for breeding season, but in recent years a small group stays year-round at PIER 39's K-Dock.