Latitudinal variation in size structure of the west coast purple sea urchin: A correlation with headlands1

Size structure of the purple sea urchin Strongylocentrotus purpuratus was sampled from central California to central Oregon (36°– 45°N). Size frequency and inferred recruitment events are correlated with major topographic features. Capes and headlands—predictable sites of upwelling and locations of cold water plumes— show size frequencies indicative of low recruitment rates. Sites without predictable upwelling or regions that are between headlands have size frequencies that indicate substantial annual recruitment.