The ecology of Strongylocentrotus franciscanus and Strongylocentrotus purpuratus

Abstract

This chapter discusses about the Strongylocentrotus franciscanus and Strongylocentrotus purpuratus, commonly known as red and purple sea urchins that are important species to the structure of kelp forest communities throughout their long ranges along the west coast of North America. Both animals are exploited for human consumption, and the red urchin is the basis of a major fishery. Purple urchins are widely used for fertilization and developmental biology studies, as well as for human food. As a result, their ecological, economic, and scientific importance, these are probably two of the best known echinoid species in the world. Red and purple urchins have overlapping spawning seasons. Despite extensive overlap in their vertical range, purple urchins are more abundant in shallow, waves wept areas and reds in more sheltered sites; the density of purples decreases with depth whereas reds increase with depth. Nevertheless, both species are found together on reefs throughout kelp forest depths, and their broad distributions suggest similar environmental tolerances.