Northeast Marine Introduced Species (NEMIS) - Print Edition

Introduced Species of Concern in the Northeast


The list of introduced species provided in this section focuses on organisms that are reported in the Northeast (from Maine to New York City), although many extend their range both to the north and south.

Not all of the introduced plants, animals, and small organisms that are reported in the northeast are identified in this list. We highlight plants and animals that:

  • can be seen with the naked eye or a magnifying glass in the field,
  • are considered a nuisance or invasive species
  • can be readily identified compared to native species
  • and/or are widespread

We have identified the probable and potential pathways for each species taking into account the eggs, larval, juvenile and adult life history characteristics. Thus, this list is by no means complete, even for species found in estuarine and marine environments. Brackish water plants and animals are not included.


Introduced species "are those that have been transported by human activities-intentionally or unintentionally- into a region in which they did not occur in historical time and are now reproducing in the wild." (See Introduced Species in U.S. Coastal Waters, James Carlton, 2001.) Other words used to denote introduced species are non-native, non-indigenous, alien, exotic, and foreign.

Invasive species, on the other hand, are "species that are non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health." (See Invasive Species Definition Clarification and Guidance White Paper, Invasive Species Advisory Committee (ISAC), 2006.)

Cryptogenic refers to a species that is neither native nor introduced, for example species that may be found on both sides of the Atlantic but that was not likely to have arrived at both coasts without human interference.