American lobster

Recognize an American lobster

It is not entirely easy to distinguish the American lobster (Homarus americanus) from the European lobster (Homarus gammarus), as both species can vary in appearance.

The most obvious sign that it is an American lobster is that the rostrum has one or two additional small spines. The European lobster has a rostrum without additional spines. The spots on the head of a European lobster are completely white, whereas the spots on the head of an American lobster are more yellow. The body colour can vary considerably, but generally, an American lobster is more brownish, especially on the tail lobes (the five plates along the tail). If they have a brownish tone on the underside, it is likely an American lobster (see image). If they are blue or brown, it is more likely to be a European one.

Why is the American lobster a threat?

Diseases

American lobsters can carry infectious diseases and parasites that can spread to the European lobster. For example, the bacterial disease Gaffkemia, which is 100% lethal to European lobsters, and the shell disease can cause significant damage to the shell and, in severe cases, also lead to the death of the lobster. These diseases do not affect the American lobster as severely as the European one, but they are life-threatening to the European.

Competition

American lobsters live in the same types of environments as the European lobster. Therefore, there is a significant risk that they could become competitors for shelters, food, or reproductive partners.

Hybridisation

In the Skagerrak, American and European lobsters have already produced offspring together, but it is still unknown what consequences this may have if hybrids spread in our waters.

Since American lobsters can also live at depths of several hundred metres, they can avoid being caught in traps. This means they can grow undisturbed, and the establishment of American lobsters in Swedish waters would be very difficult to stop.

Report it!

The American lobster has not yet established itself as an alien species in Swedish waters. Therefore, it is especially important that you contact the Institute of Marine Research (SLU) in Lysekil immediately if you catch a suspected American or sick lobster.

What to do:

• If you catch a suspected American lobster or one that appears diseased, call SLU’s Institute of Marine Research in Lysekil right away—regardless of the lobster’s size or whether it’s carrying eggs.
• The Institute of Marine Research emergency line: +46 10-478 40 48
• The staff at the Institute of Marine Research will assess your catch, and if the find is relevant, you will be granted permission to bring the lobster ashore.
• SLU offers a reward of 800 SEK per kilo for lobsters suspected to be American, after approval by phone.
• Place the lobster in a plastic bag, keep it cool, and either deliver it to the Institute of Marine Research or store it in a refrigerator until SLU staff can collect it.

Where does the American lobster come from?

The American lobster is found along the east coast of North America (USA and Canada) and is often imported—alive—to Europe and Sweden. Natural migration from North America is entirely ruled out.

How does the American lobster spread to Swedish waters?

American lobsters may be deliberately released or escape from illegal sea pens. Some captured specimens in Sweden have still had claw bands from North American exporters. In Sweden, it is illegal to store live imported lobsters in the sea.

Make a difference

Prevent further spread in Swedish waters – do not release or store American lobsters in the sea!

How many American lobsters have been caught?

Since the first reports in 2008, a total of 36 American lobsters have been recorded between Marstrand and Smögen.
- 23 were caught in 2014, 19 of them in Gullmarsfjorden.
- 5 were reported in 2015
- 3 in 2016, 2 of which were also from Gullmarsfjorden.
- No American lobsters have been reported since 2017.

SLU’s response and work on American lobsters is carried out on behalf of the Swedish Agency for Marine and Water Management, which monitors the spread of invasive species in marine and freshwater environments.