American lobster

Homarus americanus


Photo credit: ©Institute of Marine Research, Bergen, Norway
Homarus americanus
  • The American lobster is generally an olive green or green-brown colour, and red, albino and blue individuals have been observed. Orange, red, dark green or black speckles may be present, along with a blue tinge at the joints.
  • They have a pair of claws, one being a large crushing claw and the smaller one being the cutting claw.
  • There are spines on their underside, with males having sharp ones, and females having blunt ones.
  • The typical length is around 25cm, with a maximum length of 64cm. Males are bigger in size and weight than females.
  • They are long-lived and have a high reproductive potential.
  • Mated females may produce multiple clutches in the two years following mating, meaning that the population has the potential to grow significantly from one female.

Origin and Worldwide Distribution:
  • This species is native to the Atlantic Ocean around North America.
  • They have been introduced in small numbers to Japan (into captivity), and have been caught infrequently in Iceland, Denmark, Norway, Sweden and the United Kingdom.

Potential or Known Impacts:
  • The American lobster is a marine species, surviving on the bottom of the ocean (benthic zone). They can be highly adaptable to new ocean habitats, and may have the potential to move into new areas from an introduced range.
  • They have a wide range of food stuffs, ranging from algae and plant material to fish, sea urchins and clams.
  • They may have the potential to adapt to new food stuffs if introduced into a new area.
  • American lobsters may also transfer any bacterial disease (Gaffkaemia, or Epizootic Shell Disease) which they carry, onto native stocks. 

How could it get here?
  • It could potentially get here accidentally from fishery escapes or through intentional releases.

Is it found in Ireland or Northern Ireland?
  • Not present in Ireland or Northern Ireland.

You can help by reporting any sightings:  If possible, when submitting your record please include photos of key identification features.
Methods For Prevention:
  • Follow the guidelines of the 'Retain and Report' campaign.
  • If you think you have incidentally caught an American lobster, do not return it to the water.
  • If you see some of these on sale in your local area or suspect that some may have escaped into the sea in your area, please report your sightings/suspicions, including any photographs.
  • Identification can be difficult, so we would encourage you to report all sightings, even if you are not certain of the identity. If possible, try to include photos of key identification features.

Further Resources:
A 'Retain & Report' awareness campaign was launched in Northern Ireland to increase awareness amongst our fishing fleet and to encourage reporting of any suspected American lobsters. Similar campaigns were launched in Scotland and England in 2020. Further information can also be found on the:

Species Related Files:

Invasive Species Ireland

Invasive Species Ireland