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| Courtney Greiner, SITC Fisheries staff, weighs and measures green sea urchins. Photo credit: J. Barber |
The red sea urchin (Mesocentrotus franciscanus) and the green sea urchin (Strongylocentrotus droebachiensis) occur in large numbers throughout the Strait of Juan de Fuca, Admiralty Inlet, and the San Juan Islands but are also found in the inland waters of Puget Sound. Red urchins live primarily in rocky habitat at depths up to 400 ft while green urchins move around in larger groups on gravel, sand, and muddy habitats at depths that range from the intertidal to >3,000 ft. Sea urchins graze actively on seaweed using sharp jaw parts (found in a structure called Aristotle's lantern) to chew up kelp, a favorite food source.
These animals are prized for their roe which reaches peak quality in fall and winter months. This dive fishery supports a large overseas market with some product being shipped live and others being processed and cured prior to shipping. Dive harvest is restricted to harvest-by-hand only. Green sea urchins must be >2.25 inches in diameter to be legally harvested and red sea urchins must be >3.25 inches but under 5 inches in diameter. The management year for sea urchins goes from September 1 through August 31 the following year, but most of the harvest occurs during fall and winter months.
Swinomish Fisheries staff conduct subtidal red sea urchin surveys every four years in Washington state commercial sea cucumber harvests Districts 1 and 2. Surveys consist of Swinomish scientific divers recording counts of red sea urchins along a 3 ft wide transect ranging from depths of 70 to 15 ft. Transects fall on every 3.1 miles of high density red sea urchin habitat shoreline. Survey data is then used to develop a biomass estimate for each district. Green sea urchins are not surveyed in the same manner as red sea urchins due to their mobile nature and herd-like movements. As a result, green sea urchins are considered "passively managed" species by fisheries co-managers in that available biomass and fishing quotas are determined by previous levels of harvest.