Invasive Species

Invasive species are organisms which are 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Invasive species are a principal threat to native biodiversity of an ecosystem. As human disturbance of an ecosystem increases, the percentage of invasive species tends to increase, replacing native species and degrading native biological communities and habitats. By tracking invasive species in Narragansett Bay, we can track impacts to native estuarine biodiversity and, by implication, the health of the Bay ecosystem.
In the Narragansett Bay Region (NBR), invasive species are increasingly prevalent in terrestrial, aquatic and estuarine environments. In 2000 and 2003, NBEP and partners conducted a “Rapid Assessment Survey” of marine invasive species in Narragansett Bay. The team studied local “fouling organisms”—plants and animals which attach to pilings, docks and other underwater structures. This work produced the most complete information to date on invasive species in Narragansett Bay. The study suggests that up to 26% of the Bay’s fouling community is comprised of non-native species.

One invader already here in large numbers is the Asian shore crab. Although this species was first identified in Narragansett Bay less than 15 years ago, today it is the most common crab along many of our shorelines, and can be found by turning over nearly any rock in shallow estuarine water.

Another crab which is likely to appear in southern New England waters in the near future, and can be very harmful to native species and habitats is the Chinese mitten crab. This species invaded Europe during the early 1900’s and the U.S. West Coast during the 1990’s, and has become abundant in both areas. On the U.S. East Coast, the crabs first appeared in Chesapeake Bay in 2005, and were found in the Hudson River in 2007. Chinese mitten crabs dig extensive burrows in riverbanks, which can accelerate erosion. In NBR, the most vulnerable areas are likely to be rivers which are tidal in their lower reaches, such as the Taunton, Seekonk, Woonasquatucket and Pawcatuck, as well as smaller tidal systems such as Buckeye Brook.

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