California Sea Grant College Program

Fish communities at sub-tidal reefs and kelp beds at Santa Cruz Island in the Santa Barbara Channel change in response to shifts in oceanic conditions associated with the Pacific Decadal Oscillation (PDO), a long-lived El Niño-like pattern of variability in the northern Pacific Ocean. During the “warm” phase of the PDO, there is a greater abundance of “southern” fish species and a concomitant decrease in fishes normally associated with more northerly waters. The opposite occurs during “cool” periods.