Green Sea Urchins in Maine

In Maine, the green sea urchin (Strongylocentrotus droebachiensis) plays a critical ecological role in our coastal marine ecosystems, particularly in kelp forests. Herbivores by preference, they graze on algae, including kelp, which can significantly shape the structure of underwater habitats. Urchin barrens are formed when large populations of urchins overgraze on kelp and other algae, preventing their regrowth and creating an ecosystem dominated by bare rock and sparse marine life, rather than lush kelp forests. Urchins have a hard, spiny test (shell) for protection and a unique feeding structure called Aristotle's lantern for scraping algae. They reproduce by broadcast spawning in early spring, releasing eggs and sperm into the water for external fertilization. Maine's urchin populations have declined in the past 25 years due to overfishing, disease and changes in the environment. A significant driver of overfishing is the demand for urchin roe, or "uni," a delicacy in Japan and other parts of the world, where it is highly valued for its rich, creamy texture and unique flavor.

Resource Monitoring

The Maine Department of Marine Resources (MEDMR) has conducted a benthic dive survey since 2001, collecting data on urchin size, abundance, benthic habitat, basic algal cover, and the presence of invasive species. The inception of this survey was a joint effort between industry members, state scientists, policy makers, and university researchers. The Maine coast was broken into 9 regions for surveying based on fishing pressure and commercial landings value.

Sea urchin dive sites — Maine DMR green sea urchin dive survey regions

Urchin harvesters helped MEDMR scientists pick sentinel sites for the dive survey, based on industry members' observations and recommendations. Each region is comprised of 5 sentinel sites and 11 random sites picked new every year, with a total of 16 sites per region. This collaborative survey uses two divers to assess each site: one MEDMR scientist and one commercial urchin diver. This survey allows the State to monitor green sea urchin populations, as well as track changes in our benthic ecosystems.

Request Dive Survey Data or Specimens Here

Urchin Disease

There are several diseases that affect urchins in the Gulf of Maine, the most common are listed below. Overall, these diseases have significant impacts on the health of green sea urchin populations and the marine ecosystems they help shape. They are often interconnected with broader environmental changes, such as ocean warming and pollution, making effective monitoring, management and conservation efforts crucial.

Sea Urchin Wasting Syndrome (SUWS) remains the most prominent disease affecting green sea urchins in the Gulf of Maine, with significant impacts in the 1990s and early 2000s. The disease is linked to environmental stress and the presence of pathogenic bacteria.
Parasitic infections, particularly from Haplosporidium, have been implicated in affecting the reproductive health and digestive systems of sea urchins. These infections may not be as widespread but contribute to population stress.
Bacterial infections caused by Vibrio species also pose a serious threat, particularly under warm-water conditions, exacerbating tissue degradation and leading to large die-offs. If you see urchins with signs of disease, please take a picture, record the location and contact Lulu Bates at: elija.d.bates@maine.gov

Maine.gov

Maine Department of Marine Resources

Green Sea Urchins in Maine

Resource Monitoring

Urchin Disease

Survey Reports: Monitoring Maine's Sea Urchin Stock

Maine Sea Urchin Research

Reference Articles