Help stop the spread of non-native kelp Undaria pinnatifida along the West Coast

We need your help to find and respond to new outbreaks

The non-native kelp Undaria pinnatifida is a quick-growing, opportunistic non-native kelp that is a “least-wanted” pest species around the world. Uncontrolled, Undaria can become a fouling species on ship hulls, nets, fishing gear, moorings, ropes ,docks and aquaculture species and structures. Because of its quick growth and large size, it is also capable of having a profound influence on the ecosystem, by competing with native seaweeds for space and light.

Undaria was first reported from the LA-Long Beach Harbor in 2000. It has been found in numerous marinas in Southern California, including a mooring at Catalina Island. It became established in Monterey Harbor in 2001. For eight years, Monterey was its northernmost extent. In May 2009, we found small populations at Pillar Point Harbor in Half Moon Bay and at two sites in San Francisco Bay. Based on its environmental tolerances, Undaria could potentially range from Southeast Alaska to Baja California. It can spread by hitchhiking on boats, anchors, floats and aquaculture gear.

Your help is needed to report new sightings! Please report any sightings along with key details, as outlined below. Early detection can help prevent the further spread of this invasive species. You can also assist by inspecting your boat and slip and removing Undaria if you find it, especially before getting underway and by joining removal efforts

If you find Undaria

Please report suspected Undaria by signing up and following instructions to upload photos and observation notes here (Sign Up Link) or email us your sighting information at marineinvaders@gmail.com. We will reply to each report and may ask about any specimens that you may have collected.

For other questions, you can also contact us at 415 435 3528.