American Lobster (Homarus americanus)
CrustaceanMarineNorth Atlantic
An adult American lobster on the seafloor off Dutch Island, Rhode Island, in December 1996.
Image: Rick Wahle / NOAA Photo Library, CC BY 2.0, via Wikimedia Commons.
Overview
The American lobster (Homarus americanus) is a clawed crustacean of the northwest Atlantic, living on the seafloor along the coast of North America from Labrador or Newfoundland to North Carolina.
It has ten legs, and the first pair forms two unequal claws: a big-toothed crusher for pulverizing shells and a finer-edged claw for tearing or cutting. Living lobsters are mostly olive-green, greenish-brown or blackish-green, sometimes flecked with red, orange or black; they are not red until cooked.
Lobsters commonly caught are about 25 cm long and weigh about 0.5 kg. How large the biggest grow is disputed: published maximum lengths run from 60 cm to 114 cm, and maximum weights from 1.7 kg to 44 pounds.
Habitat & Range
American lobsters live on the bottom, from the shoreline to the outer continental shelf, wherever a burrow or crevice gives them cover. They prefer rocky ground but also use sand and mud, where they can burrow, and young lobsters seem to prefer settling among cobble. Offshore they are most abundant along the edge of the continental shelf near underwater canyons. The largest populations are in the Gulf of Maine and, in Canada, around Nova Scotia and the southern Gulf of St. Lawrence.
Sources differ on depth: one says lobsters are generally found shallower than 50 m, another that they are more abundant in deeper water, and stated maximum depths range from 365 m to 800 m.
Diet
Adults feed mainly on bottom animals — crabs, clams, mussels, snails, worms, sea urchins, sea stars and fish — and also eat algae and eelgrass; larvae and postlarvae eat zooplankton. Most feeding happens at night, and after molting a lobster eats voraciously, often devouring its own cast shell.
Accounts of how lobsters choose food differ: one describes an opportunistic feeder whose diet follows the prey available, another a possibly selective feeder that keeps its diet steady when prey numbers change, and a third mostly a scavenger that can also catch live prey. Lobsters eating other lobsters has never been recorded in the wild, although it happens in captivity.
Behavior
American lobsters are solitary and territorial, and individuals rarely interact. They are nocturnal, spending most of the day in a burrow or under rocks, out of reach of predators — mainly cod — and wandering the seafloor at night in search of food, sometimes into the intertidal zone at high tide.
Studies of lobsters introduced into a community show a social hierarchy, in which a higher-status male secures a shelter and can mate with several females. Most lobsters stay within a home range of about 5–10 square km. Small coastal lobsters travel little and larger ones may travel extensively, while large offshore lobsters make seasonal migrations, including moves inshore to reproduce; other accounts describe migration as limited or absent.
Human Interaction & Conservation
In fishery assessments the Gulf of Maine and Georges Bank lobsters are treated as a single biological unit, because large females migrate seasonally between the two areas. Outside its range the American lobster turns up sporadically in northern European waters, probably as discarded, escaped or deliberately released live animals, which raises concern about hybridization, competition or disease transfer to the native European lobster; it has not become established in Japan.
IUCN's global assessment lists the American lobster as Least Concern (2011).
Reproduction & Life Cycle
Lobsters usually mate after the female molts, while her shell is soft; mating has to happen within 48 hours of the molt, and females are ready to mate at about five years old. The female stores the sperm until she releases her eggs — for up to a year by one account, up to two years by others — and then carries the fertilized eggs under her tail for 9 to 11 months.
Clutch size grows with the female: from 5,000 to more than 100,000 eggs by one account, while another gives about 3,000 eggs for an 18 cm female and around 75,000 for a 45 cm one. Eggs hatch from mid-May to mid-June, and the larvae are planktonic, swimming at or near the surface, for four stages before settling on the bottom at the fifth.
Lobsters are long-lived, but their age is hard to measure because molting leaves no evidence of it; scientists believe some may live to 100 years.
Sourced facts
Each value below is traced to the specific reference that states it. Open a row's evidence to see the source, where to look in it, and how firmly it supports the value. Sources checked 2026-10-20.
| Fact | What the source states | Evidence |
|---|---|---|
| Distinguishing traits | Clawed crustacean with ten legs; the first pair forms two unequal claws, a big-toothed crusher for pulverizing shells and a finer-edged claw for tearing or cutting. Live animals are mostly olive-green, greenish-brown or blackish-green, sometimes flecked red, orange or black; not red until cooked.The crushing claw is usually the larger one. The first three pairs of walking legs end in true pincers; the enlarged first pair is massive, flattened, unequal and smooth. Color is variable: often a yellow or yellowish-red background mottled with green or blue, with an overall dark appearance. | Matches source · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Animal Diversity Web (University of Michigan Museum of Zoology), Fisheries and Oceans Canada, Virginia Institute of Marine Science (William & Mary), Multispecies Research Group — how we knowNOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Animal Diversity Web (University of Michigan Museum of Zoology)
Fisheries and Oceans Canada
Virginia Institute of Marine Science (William & Mary), Multispecies Research Group
|
| Geographic range | Found in the northwest Atlantic along the coast of North America, from Labrador or Newfoundland south to North Carolina; in U.S. inshore waters, most abundant from Maine through New Jersey. Elsewhere it turns up sporadically in northern European waters and has not become established in Japan.sources disagreeThe largest populations are in the Gulf of Maine and, in Canada, around Nova Scotia and the southern Gulf of St. Lawrence. One database lists introductions in Ireland, Norway and Japan; the northern European occurrences are probably discarded, escaped or deliberately released live animals, and raise concern about hybridization, competition or disease transfer to the native European lobster. | Sources disagree · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Fisheries and Oceans Canada, World Register of Marine Species (WoRMS, hosted by VLIZ), Deep-Sea subregister view of the same record, SeaLifeBase, Atlantic States Marine Fisheries Commission — how we knowWhat each reading says
Sources place the range limits differently: the southern limit is Cape Hatteras (NOAA) or Rich Inlet near Wilmington, North Carolina (WoRMS), and the northern limit is Labrador (NOAA, WoRMS), Newfoundland (SeaLifeBase) or the waters of Newfoundland and Labrador (DFO). NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Fisheries and Oceans Canada
World Register of Marine Species (WoRMS, hosted by VLIZ), Deep-Sea subregister view of the same record
SeaLifeBase
Atlantic States Marine Fisheries Commission
|
| Habitat | Lives on the seafloor from the shoreline to the outer continental shelf wherever a burrow or crevice gives cover; prefers rocky bottoms but also uses mud and sand. Sources differ on the depths it usually occupies and on its maximum depth.sources disagreeNOAA: coastal lobsters like rocky areas but are sometimes found in mud bottoms where they can burrow; offshore populations are most abundant along the continental shelf edge near underwater canyons. ADW: also found in sandy and muddy areas; young lobsters seem to prefer settling in areas with cobble. | Sources disagree · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Animal Diversity Web (University of Michigan Museum of Zoology), Fisheries and Oceans Canada, World Register of Marine Species (WoRMS, hosted by VLIZ), Deep-Sea subregister view of the same record, SeaLifeBase — how we knowWhat each reading says
Depths disagree: DFO says generally shallower than 50 m and SeaLifeBase usually 4-50 m, while ADW says the species is more abundant in deeper waters; maximum depth is 365 m (ADW), 480 m (SeaLifeBase), observed beyond 500 m (DFO) or 800 m (WoRMS), and NOAA says lobsters are common offshore to 2,300 feet. NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Animal Diversity Web (University of Michigan Museum of Zoology)
Fisheries and Oceans Canada
World Register of Marine Species (WoRMS, hosted by VLIZ), Deep-Sea subregister view of the same record
SeaLifeBase
|
| Diet | Adults eat mainly bottom animals (crabs, clams, mussels, snails, worms, sea urchins, sea stars, fish) plus algae and eelgrass; larvae and postlarvae eat zooplankton. Sources differ on whether it is an opportunistic, a possibly selective or a mainly scavenging feeder.sources disagreeMost feeding happens at night. After molting, lobsters eat voraciously, often devouring their own recently vacated shells. Lobsters eating other lobsters has never been recorded in the wild, but happens in captivity. | Sources disagree · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Animal Diversity Web (University of Michigan Museum of Zoology), SeaLifeBase, Virginia Institute of Marine Science (William & Mary), Multispecies Research Group — how we knowWhat each reading says
Feeding strategy is described differently: NOAA calls lobsters opportunistic feeders whose diet follows prey availability; SeaLifeBase calls the species possibly a selective feeder that keeps its diet composition despite changes in prey availability; ADW says it is usually a scavenger that can also capture prey. NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Animal Diversity Web (University of Michigan Museum of Zoology)
SeaLifeBase
Virginia Institute of Marine Science (William & Mary), Multispecies Research Group
|
| Body size | Commonly about 25 cm long; published maximum lengths range from 60 cm to 114 cm, the latter stated as total length.sources disagreeOnly one source names the measure (total length, male or unsexed); the others do not say which length they mean. The 25 cm figure is the size of lobsters commonly caught. | Sources disagree · Animal Diversity Web (University of Michigan Museum of Zoology), SeaLifeBase, Fisheries and Oceans Canada, Virginia Institute of Marine Science (William & Mary), Multispecies Research Group — how we knowWhat each reading says
Figures for the largest lobsters disagree: DFO says lobsters can grow to 60 cm, the FAO text on VIMS says exceptionally over 640 mm, ADW gives up to 1.1 m and SeaLifeBase a maximum of 114 cm total length. Animal Diversity Web (University of Michigan Museum of Zoology)
SeaLifeBase
Fisheries and Oceans Canada
Virginia Institute of Marine Science (William & Mary), Multispecies Research Group
|
| Body mass | Lobsters commonly caught weigh about 0.5 kg; published maximum weights range from 1.7 kg to 44 pounds.sources disagreeA newly hatched lobster weighs less than one tenth of a gram. | Sources disagree · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Animal Diversity Web (University of Michigan Museum of Zoology), Fisheries and Oceans Canada, SeaLifeBase — how we knowWhat each reading says
Maximum weight disagrees: NOAA says up to 44 pounds; DFO over 18 kg; ADW gives 20 kg in one passage and up to 10 kg for full adults in another; SeaLifeBase lists a max. published weight of 1.7 kg. NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Animal Diversity Web (University of Michigan Museum of Zoology)
Fisheries and Oceans Canada
SeaLifeBase
|
| Lifespan | Long-lived; scientists believe some American lobsters may live to be 100 years old, but exact age is hard to determine because molting leaves no evidence of age.The 100-year figure is what scientists believe for some individuals, not a measured or typical lifespan; neither source gives a captive lifespan. | Matches source · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Fisheries and Oceans Canada — how we knowNOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Fisheries and Oceans Canada
|
| Activity pattern | Nocturnal: spends most of the day in a burrow or under rocks and in crevices, and wanders the seafloor at night in search of food, sometimes entering the intertidal zone at high tide.Lobsters stay among rocks by day to avoid predators, mainly cod, and leave the burrow only if food is nearby. | Matches source · Animal Diversity Web (University of Michigan Museum of Zoology), Fisheries and Oceans Canada — how we knowAnimal Diversity Web (University of Michigan Museum of Zoology)
Fisheries and Oceans Canada
|
| Social structure | Solitary and territorial; individuals rarely interact. Studies of lobsters introduced into a community show a social hierarchy, in which a higher-status male secures a shelter and can mate with several females.A lobster can recognize one it has met before for up to two weeks, possibly by the chemicals they excrete. | Matches source · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Atlantic States Marine Fisheries Commission, Animal Diversity Web (University of Michigan Museum of Zoology) — how we knowNOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Atlantic States Marine Fisheries Commission
Animal Diversity Web (University of Michigan Museum of Zoology)
|
| Reproduction | Mates after the female molts; she stores the sperm, then carries the fertilized eggs under her tail for 9 to 11 months. Eggs hatch in late spring or early summer, and larvae pass four free-swimming stages before settling. Sperm-storage time and clutch size differ by source.sources disagreeSperm is deposited in soft-shelled, recently molted females; mating must occur within 48 hours of the female's molt, and females are ready to mate at about 5 years of age. Eggs hatch from mid-May to mid-June; larvae are planktonic for four stages, swimming at or near the surface, and sink to the bottom at the fifth. One account gives about 10 to 11 months for carrying eggs. | Sources disagree · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Atlantic States Marine Fisheries Commission, Animal Diversity Web (University of Michigan Museum of Zoology) — how we knowWhat each reading says
Sperm storage: NOAA says up to a year, while ASMFC (as long as two years) and ADW (eggs spawned up to two years after mating) allow longer. Clutch size: NOAA gives 5,000 to more than 100,000 eggs depending on size; ADW gives about 3,000 eggs for an 18 cm female, below NOAA's lowest figure. NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Atlantic States Marine Fisheries Commission
Animal Diversity Web (University of Michigan Museum of Zoology)
|
| Movement | Usually stays within a home range of about 5-10 square km. Small coastal lobsters travel little and larger ones may travel extensively; large offshore lobsters make seasonal migrations, including inshore moves to reproduce. Other accounts say migration does not occur or is limited.sources disagreeEgg-bearing females move inshore to hatch their eggs in late spring or early summer. Large lobsters in southern inshore areas may move to deeper, cooler water seasonally or permanently. Because large females migrate seasonally between the Gulf of Maine and Georges Bank, those two stock areas were combined into a single biological unit. | Sources disagree · NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration), Atlantic States Marine Fisheries Commission, SeaLifeBase, Virginia Institute of Marine Science (William & Mary), Multispecies Research Group — how we knowWhat each reading says
NOAA and ASMFC describe seasonal migrations by large and offshore lobsters (NOAA: 50 to 190 miles in spring), whereas the FAO-derived texts on SeaLifeBase and VIMS say migration does not occur or occurs only on a limited scale. NOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)
Atlantic States Marine Fisheries Commission
SeaLifeBase
Virginia Institute of Marine Science (William & Mary), Multispecies Research Group
|
| Conservation status | Least Concern (LC), global assessment, 2011 | Matches source · IUCN Red List of Threatened Species — how we knowIUCN Red List of Threatened Species
|
References for the facts above
- GovernmentNOAA Fisheries (U.S. National Oceanic and Atmospheric Administration)Supports: Appearance, Biology and Where They Live sections: claws and color, maximum weight, lifespan belief, molting, reproduction, diet, range, habitat, solitary and territorial behavior, movements. Retrieved 2026-10-20.Limitations: U.S. agency page; its fishery, stock-status and regulation sections describe U.S. stocks only and were not used for biology; weight is given only as a maximum; the 100-year lifespan is presented as what scientists believe.
- GovernmentAtlantic States Marine Fisheries CommissionSupports: Life History section: solitary and territorial behavior, home range, seasonal migrations, sperm storage, egg carrying, hatching season, larval stages, stock structure. Retrieved 2026-10-20.Limitations: U.S. interstate fisheries-management body; most of the page is management and stock assessment for U.S. stocks; the biology is a short unsourced Life History summary.
- GovernmentFisheries and Oceans CanadaSupports: Habitat and Species Description sections: range, depth, largest populations, nocturnal habit, color, legs and claws, length, weight, long life, molting. Retrieved 2026-10-20.Limitations: Brief profile (date modified 2024-04-29); length and weight are single large-animal figures and the length measure is not named; the URL redirects to the www. host.
- UniversityAnimal Diversity Web (University of Michigan Museum of Zoology)Supports: Geographic Range, Habitat, Physical Description, Reproduction, Behavior and Food Habits sections. Retrieved 2026-10-20.Limitations: Student-written account (D. Lydon), last updated 2003-05-13; the length measure is not named; it gives two different maximum weights (20 kg and up to 10 kilograms) in different passages.
- ReferenceWorld Register of Marine Species (WoRMS, hosted by VLIZ), Deep-Sea subregister view of the same recordSupports: Distribution and Habitat notes (native range, depth, substrate) and introduced-species entries. Retrieved 2026-10-20.Limitations: Same DecaNet/WoRMS record content as the main taxdetails page used for identity, whose single-segment URL fails the selfcheck record-depth rule; the distribution and habitat notes are marked unreviewed; introduced-species entries come from regional databases, and entries labeled Ukraine cite GB legislation, so some labels look unreliable.
- ReferenceSeaLifeBaseSupports: Environment, Distribution, Size/Weight, Biology and Life cycle fields: total length, max. published weight, depth range, introductions, diet, migration. Retrieved 2026-10-20.Limitations: Database summary compiled mainly from Holthuis 1991 (FAO catalogue) and other cited references; its max. published weight of 1.7 kg is far below the other sources' maximums; a cookie-consent banner is shown but the full content is served in the HTML.
- UniversityVirginia Institute of Marine Science (William & Mary), Multispecies Research GroupSupports: Size, Diagnostic characters, Habitat/biology and Distribution text. Retrieved 2026-10-20.Limitations: Species text is reproduced from FAO identification guides (Carpenter 2002), credited on the page, not original VIMS research; the length measure is not named; overlaps with SeaLifeBase's FAO-derived content.
- ReferenceIUCN Red List of Threatened SpeciesSupports: The global Red List category and the year of the assessment. Retrieved 2026-10-20.Limitations: Read from the Red List export IUCN publishes to GBIF; iucnredlist.org itself does not answer automated reads. Categories are reassessed over time.
Frequently Asked Questions — American Lobster
Are live American lobsters red?
No. Living lobsters are mostly olive-green, greenish-brown or blackish-green, sometimes flecked with red, orange or black. They are not red until cooked.
Why are a lobster's two claws different?
The first pair of legs forms two unequal claws: a big-toothed crusher for pulverizing shells and a finer-edged claw for tearing or cutting. The crushing claw is usually the larger one.
How long do American lobsters live?
They are long-lived, but their exact age is hard to determine because molting leaves no evidence of age. Scientists believe some may live to 100 years.
How big do American lobsters get?
Lobsters commonly caught are about 25 cm long and weigh about 0.5 kg. Published maximums vary widely, from 60 cm to 114 cm in length and from 1.7 kg to 44 pounds in weight.
Sources and further reading
Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.
- GovernmentNOAA Fisheries (U.S. National Oceanic and Atmospheric Administration) — American lobster species page (biology sections) — Appearance, Biology and Where They Live sections: claws and color, maximum weight, lifespan belief, molting, reproduction, diet, range, habitat, solitary and territorial behavior, movements
- GovernmentAtlantic States Marine Fisheries Commission — American lobster life history — Life History section: solitary and territorial behavior, home range, seasonal migrations, sperm storage, egg carrying, hatching season, larval stages, stock structure
- GovernmentFisheries and Oceans Canada — American lobster species profile — Habitat and Species Description sections: range, depth, largest populations, nocturnal habit, color, legs and claws, length, weight, long life, molting
- UniversityAnimal Diversity Web (University of Michigan Museum of Zoology) — Homarus americanus (American lobster) species account — Geographic Range, Habitat, Physical Description, Reproduction, Behavior and Food Habits sections
- ReferenceWorld Register of Marine Species (WoRMS, hosted by VLIZ), Deep-Sea subregister view of the same record — Homarus americanus, AphiaID 156134 — Distribution and Habitat notes (native range, depth, substrate) and introduced-species entries
- ReferenceSeaLifeBase — Homarus americanus species summary — Environment, Distribution, Size/Weight, Biology and Life cycle fields: total length, max. published weight, depth range, introductions, diet, migration
- UniversityVirginia Institute of Marine Science (William & Mary), Multispecies Research Group — American lobster species of interest (FAO text) — Size, Diagnostic characters, Habitat/biology and Distribution text
- ReferenceIUCN Red List — Homarus americanus assessment — The global Red List category and the year of the assessment