Red Sea Urchin

by Scott Boyd

The red sea urchin (Strongylocentrotus franciscanus) is a large, spiny, urchin that lives on rocky seafloors. It can be found off the west coast of North America, from Alaska to the Baja peninsula. It lives in depths from the intertidal zone down to about 300 feet.

The red sea urchin can grow to as much as 10 inches across; the spines are about 1/2 the size of the body (or test). The color ranges from red to dark-purple (juveniles are green). Adult sea urchins have five-sided radial symmetry and are related to sea stars. Their spines are used for protection, for moving, and for trapping drifting algae to eat. Their primary diet consists of kelp, decaying animal matter, algae, dead fish, sponges, mussels, and barnacles.

 Sea urchins in turn are eaten by crabs, sunflower stars, snails, sea otters, fish, and people.  They are also  a favorite food  of our friendly local population of Wolf Eels.

 Red sea urchins reach sexual maturity at the age of two years. Females and males release their gametes into the ocean where fertilization occurs in the open during the months of January, February and March.

  Sea urchins are commercially harvested off of our coast (especially in California), primarily for the Japanese market, where it is a common ingredient in sushi. Japan buys over 6,000 tons of sea urchins at a total value of 251 million dollars per year.