Sea urchin recruitment patterns and implications of commercial fishing.

Coexisting sea urchins Strongylocentrotus purpuratus and S. franciscanus exhibit different recruitment patterns. Juveniles of the former species are found in a variety of habitats, whereas juveniles of the latter occur almost exclusively under the spine canopy of conspecific adults. The commercial harvest of S. franciscanus thus seems to affect nursery grounds as well as the reproductive potential of exploited populations.