Ta. Ebert et al., SETTLEMENT-PATTERNS OF RED AND PURPLE SEA-URCHINS (STRONGYLOCENTROTUS-FRANCISCANUS AND STRONGYLOCENTROTUS-PURPURATUS) IN CALIFORNIA, USA, Marine ecology. Progress series, 111(1-2), 1994, pp. 41-52
Weekly settlement of red and purple sea urchins (Strongylocentrotus fr
anciscanus and S. purpuratus) was documented at sites in northern and
southern California (USA) for 4 settlement seasons from 1990 to 1993.
Newly settled sea urchins (<0.5 mm) were collected from standardized s
ettlement surfaces (scrub brushes), identified and counted, There was
marked seasonality in settlement. For both species, most settlement oc
curred during one to several episodes between February and July of eac
h year. Settlement tended to be more regularly annual in southern than
in northern California and settlement densities generally were higher
in the south. This pattern is consistent with greater retention of wa
ter in the Southern California Bight and more energetic offshore advec
tion of water in northern California, S. purpuratus showed geographic
coherence in settlement whereas S, franciscanus did not. For purple se
a urchins, northern sites formed a group, a second group was formed by
sites near Santa Barbara plus a site in Orange County, and a third gr
oup was formed by 3 sites at San Diego.