Report Sightings of Caulerpa
What is Caulerpa?
The genus Caulerpa is a group of marine green algae made up of over 100 different species distributed mostly in tropical regions. There are no native Caulerpa species (spp.) in California. Caulerpa spp. grow quickly and can rapidly displace native animals, plants, and algae when they invade areas they are not from. Caulerpa spp. have a high tolerance for wide ranging environmental conditions and can reproduce asexually by rhizoid extension or fragmentation (see graphic below). In temperate waters like California, Caulerpa spp. appear to have no natural predators allowing it to grow and spread rapidly. Invasions of Caulerpa spp. are well‐documented to have aggressively displaced native species in California, Australia, and the Mediterranean.
Allowing any species of Caulerpa spp. to become established and spread within California is likely to result in significant negative socioeconomic and ecological impacts. As of January 1, 2024, it is illegal to sell, posses, import, transport, transfer or release alive any species of Caulerpa in California (Fish & G. Code §2300). Releases from aquaria, either directly into the water or indirectly through storm drains, are the most likely sources of California infestations. Since it is illegal to possess Caulerpa spp. in California for any reason, except with prior authorization by CDFW for bona fide scientific research, if you currently have Caulerpa spp. in your possession see "What should you do?" to ensure you do not spread this invasive species.
Examples of various types of Caulerpa spp. found worldwide. Any of these morphologies could be introduced to California as invasive species. Caulerpa taxifolia which is distichous, and Caulerpa prolifera which is ligulate have both been found in Califorina. Graphic from Zubia, M., Draisma, S.G.A., Morrissey, K.L. et al. Concise review of the genus Caulerpa J.V. Lamouroux. J Appl Phycol 32, 23–39 (2020).
Status of California Caulerpa Infestations
California is the only place in the world that has successfully eradicated a Caulerpa spp. invasion. Caulerpa taxifolia was found at two locations in southern California in 2000. A rapid response to map, control, and eradicate C. taxifolia in Aqua Hedionda and Huntington Harbour was conducted. The seriousness and acknowledged threat of the situation prompted an extensive and highly effective eradication project. This eradication took six years at a cost of more than seven million dollars. Although lengthy and expensive, the successful eradication led to the recovery of critically important eelgrass habitat and helped to protect California’s coastal ecosystems. See "Additional Information" at the bottom of this page for links to more detailed information on the successful C. taxifolia eradication effort in California.
During the initial Caulerpa spp. eradication effort in 2000, the Southern California Caulerpa Action Team (SCCAT) was formed. The SCCAT is an ad-hoc group made up of federal, state, and local regulators, scientists, consultants and other stakeholders who coordinate effective eradication responses to infestations and prevent the spread of Caulerpa spp. The SCCAT holds no regulatory authority allowing for a focus on aggregating resources and prioritizing deployment in the most effective way. SCCAT members also use the group to inform and coordinate management actions to ensure actions are based on the best science available and latest understanding of conditions on the ground.
The Caulerpa Control Protocol (PDF) (Protocol) was created by the SCCAT and outlines prescriptive levels of surveillance surveys based on current infestation levels. The Protocol is administered jointly by the California Department of Fish and Wildlife (CDFW) and NOAAs National Marine Fisheries Service (NMFS). Under the Protocol bottom disturbing activities in near coastal waters and enclosed bays, estuaries and harbors from Morro Bay to the U.S.-Mexico border should be surveyed unless given an exemption by CDFW/NMFS. The Protocol outlines certification requirements for surveyors and includes a required template to meet reporting requirements. When Caulerpa spp. is reported the SCCAT convenes to coordinate a rapid response plan which includes taking the following steps as rapidly as resources can be mobilized.
- Control of Infestation Site - To prevent disturbance by boat anchors and boat wakes, a newly identified Caulerpa spp. infested area will be controlled through coordination with local landowners and regulators.
- Localized Comprehensive Surveys - Intensive diver surveys are conducted covering 100% of the bottom within and surrounding the identified invasion. Divers locate, record, and map any Caulerpa spp. found.
- Treatment - The Caulerpa spp. patches are covered by trained divers with a sealed barrier that will kill the algae by exclusion from light, nutrients, and circulation.
- Posttreatment Surveys – Divers conduct additional surveys immediately following treatment and over a longer timeframe to help ensure all Caulerpa spp. receives treatment and there are no individuals remaining to repopulate the area.
- Broad Area Surveys - Diver surveys will occur in surrounding areas to determine if other areas have been invaded by Caulerpa spp.
Newport Bay Infestation
In March 2021, a new invasive species to California, Caulerpa prolifera, was discovered in Newport Bay, within China Cove. The China Cove infestation was found deeper than previous infestations and was removed using a suction dredge in July 2021. Ongoing localized surveillance efforts found small additional patches throughout 2022 into the spring of 2023 that were treated leading to zero finds of C. prolifera being recorded in June, July and September of 2023. Since that time there have been no additional Caulerpa spp. sightings in China Cove. However, two additional patches in Newport Bay were found, at Collins Isle in March 2022 and Linda Isle in January 2025. These patches have been treated using standard tarping methods to exclude light, nutrients and circulation. The significant eradication efforts appear to be working. Recent surveys have found no new growth, and the hope is that all the Caulerpa spp. has been removed in Newport Bay. This invasion has now moved to the posttreatment and broad area survey phases to confirm eradication. This includes the ongoing need to conduct high-intensity surveillance in areas not previously surveyed and to revisit infestation areas regularly. For more details, please see the Newport Bay Rapid Response Plans and Update Memos through July 2025 (PDF).
San Diego Bay Infestation
In September 2023, Caulerpa prolifera, previously identified in March 2021 in Newport Bay, was also discovered in San Diego Bay, in a small area off the Coronado Cays. Eradication efforts began immediately. Two additional patches were found in the adjacent San Diego National Wildlife Refuge in April 2024 and another small patch adjacent to previous finds was found in August 2025. All patches have been treated with the standard tarping method to exclude light nutrients and circulation, and the August 2025 patches also had rock salt added under the tarps to facilitate faster die off of live C. prolifera tissue. Current efforts are focused on treatment, postteatment surveys, and broad area surveys. This includes seeking resources to expand survey areas to ensure no patches have been missed and currently treated areas are not spreading. For more details, please see the San Diego Bay Rapid Response Plan and Survey Design through July 2025 (PDF).