Homarus americanus
(American lobster)
Crustaceans-Lobsters
Native Transplant |
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Common name: American lobster
Synonyms and Other Names: Northern lobster
Taxonomy: available through
www.itis.gov
Identification: Homarus americanus have large crusher claws on the chelipeds (first pair of legs) that are used for breaking shells. The second and third legs have smaller claws on them. The body is long and cylindrical with hard exoskeleton. The tail has fans that flare out for backwards swimming. H. americanus has two long whip-like antennas and two shorter ones near the small black eyes (Gosner 1978; Williams 1984). Adults can grow longer than 90 cm and weigh more than 20 kg. Color is highly variable, most commonly dark blue green to brown olive with green-black spots with sometimes hints of red or orange. Claws, as well as the frontal and ventral regions have orange spots (Gosner 1978; Williams 1984; Jørstad et al. 2007). H. americanus can be confused for the European lobster (Homarus gammarus). H. gammarus lacks teeth on the underside of the rostrum and is often blue black, white, or yellow with orange on the claws. Genetic testing can be used to confirm the species of lobsters as physical features can be variable (Jørstad et al. 2007).
Size: To 3 feet (90 cm).
Native Range: Northwest Atlantic Ocean, ranging from Cape Hatteras, North Carolina, to Labrador, Canada
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Alaska |
Hawaii |
Puerto Rico &
Virgin Islands |
Guam Saipan |
Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps
Nonindigenous Occurrences:
Although lobsters have been repeatedly introduced since the late 1800s along the eastern Pacific coast in California, Oregon, Washington and British Columbia , no second generation reproducing populations have resulted from any of these attempts (Carlton 1979).
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Homarus americanus are found here.
Table last updated 1/21/2026
† Populations may not be currently present.
Ecology: H. americanus inhabits depths ranging from 1 to 700 meters depending on latitude (Cobb 1976). Inshore adult populations prefer boulder or rocky habitats, and in deeper habitats with fewer rocks, adults will burrow into sediment (MacKenize and Moring 1985). They are omnivores and have been recorded eating fish, crustaceans, mollusks, algae, echinoderms, and hydroids (Cobb 1976). Female lobsters will only mate within 48 hours after molting and can store sperm for up to 15 months until eggs are laid and fertilized. Fully grown females can carry up to 80,000 eggs at a time and will carry eggs for 10-11 months on the underside of the tail (Cobb 1976).
Larvae go through four stages defined by four molts. They are free swimming for the first three stages/molts, and after the fourth molt will resemble an adult and begin to seek the bottom of the ocean, while fifth stage are completely bottom seeking, but can be observed often swimming (Cobb 1976). H. americanus goes through 20-25 molts in its lifetime and can only grow larger through molts. They can autotomize, or reflexively amputate, any of their walking legs and chelae (pincer-like claws), and can grow back any of those limbs.
Means of Introduction: Multiple attempts have been made to introduce H. americanus for aquaculture purposes to the Pacific coast of the U.S. and Canada, the southern U.S., Texas, and Japan, however none of these introduced populations successfully established. Recent occurrences, particularly in northern European waters, are most likely due to released live animals, discarded ones, or live escapes (Carlton 1979; Smithsonian Environmental Research Center 2025).
Status: Failed introduction
Impact of Introduction: Summary of species impacts derived from literature review. Click on an icon to find out more...
Despite many efforts to introduce it to new areas, the Homarus americanus has not established permanent populations outside its native range. However, its occasional appearance in northern European waters has raised concerns about potential risks to the native European lobster (Homarus gammarus), including the chance of hybridization, competition for resources, or the spread of disease (Jørstad et al. 2007; Jørstad et al. 2011).
References: (click for full references)
Carlton, J. T. 1979. History, Biogeography, and Ecology of the Introduced Marine and Estuarine Invertebrates of the Pacific Coast of North America. 904 pp.
Cobb, J. S. 1976. The American lobster: the biology of Homarus americanus.
Gosner, K.L. 1978. A field guide to the Atlantic seashore. The Peterson Field Guide Series. 329 pp.
Jørstad, Knut E.; Prodohl, P. A.; Agnalt, A.-L.; Hughes, M.;Farestveit, E.; Ferguson, A. F. 2007. Comparison of genetic and morphological methods to detect the presence of American lobsters, Homarus americanus H. Milne Edwards, 1837 (Astacidea: Nephropidae) in Norwegian waters., Hydrobiologia 590: 103-114
Jørstad, Knut Eirik; Agnalt, Ann-Lisbeth; Farestveit, Eva. 2011. In the wrong place- Alien marine crustaceans: Distribution, biology, impacts, Springer, Dordrecht, Netherlands. Pp. 625-638
MacKenzie, Chet; Moring John R. 1985. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (North Atlantic); American Lobster, Biological Report 82(11.33): 1-19
Smithsonian Environmental Research Center. 2025. National Estuarine and Marine Exotic Species Information System, https://invasions.si.edu/nemesis/species_summary/97314 Accessed on 11/19/2025
Williams, Austin B. (1984) Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States, Maine to Florida, Smithsonian Institution Press, Washington, DC.
Author:
Williams, A and W. Daniel
Revision Date: 11/19/2025
Citation Information:
Williams, A and W. Daniel, 2026, Homarus americanus: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=1087, Revision Date: 11/19/2025, Access Date: 1/21/2026
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.
