The red sea urchin is the largest sea urchin species and can reach a diameter of about 7 inches in the largest specimens. Its body is dark red to black in color with large, lighter red spines.

The red sea urchin is found on the eastern side of the Pacific ocean, along the west coast of North America down to the tip of Baja California, Mexico.

The red sea urchin mainly lives in the rocky parts of the shoreline, also called the intertidal zone and down to depths of about 525 feet.

The red sea urchin is an herbivore and feeds mainly on kelp, which is why it is often found in kelp forests.

Around San Diego, the main predators of the red sea urchin are the California spiny lobster and the California sheephead, while north of Point Conception the main predator is the sea otter.

After the eggs are released into the seawater and fertilized, larvae hatch and drift freely before settling on the seafloor and developing into young juvenile sea urchins.

By feeding on giant kelp, the red sea urchin plays an important role in the development of giant kelp forests and in shaping the structure of the entire ecosystem.