About the Data
Species records include data on invasions history, distribution, ecology, impact, and more. These data were gathered from published literature and targeted surveys. All records have undergone expert review, unless otherwise noted.
Species Profiles
NEMESIS includes detailed information on about 500 species of marine and estuarine of invertebrates and algae introduced to the United States. Each record contains information on taxonomy, distribution, ecology, and impacts, as well as references.
Clava multicornis
Clava multicornis is a sessile hydrozoan, which lacks a planktonic medusa stage. It is native to the North Atlantic, ranging from Long Island to Labrador, Iceland, the White Sea, and the Bay of Biscay. It was introduced to San Francisco Bay, California, but has not been collected there in more than 50 years. However, in 2013, extensive established colonies were found on floating docks in Coos Bay, Oregon. It can settle on a variety of substrates, including seaweeds, mollusk shells, rocks, pilings, and buoys. No impacts have been reported for this species.
Daily Invader for 2026-08-25