Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.
The Estuarine Mudcrab (Rhithropanopeus harrisii) is a small crab native to the East Coast of North America from southern Canada to Mexico. This species is able to adapt to a wide range of salinities, and introductions of this species have been documented in Europe, Japan, Venezuela, the West Coast of the United States, and even freshwater reservoirs in Texas and Oklahoma with high mineral content. The spread of R. harrisii is believed related to shipping, oyster transport, fish stocking, and bait bucket or accidental angler/boater releases. Negative impacts of introduced populations of R. harrisii on native biodiversity have been documented in the scientific literature. Impacts include reduced abundance of gastropods, small crustaceans, amphipods and isopods; elimination of chironomids; decreases in species richness and diversity; increases in nutrients and phytoplankton; and changes in community composition. R. harrisii can host white spot baculoviruses and is parasitized by the rhizocephalan barnacle Loxothylacus panopaei. It is used as a research organism in developmental, physiological and pesticide studies. In high densities, R. harrisii causes pipe fouling and economic loss to fishermen by spoiling fishes in gill nets. R. harrisii has a high climate match with the contiguous United States, especially on the Atlantic, Gulf and Pacific coasts. Certainty of this assessment is high, and the overall risk assessment category is also high.
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High Risk
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