American Lobster

Homarus americanus commonly reaches 200–610 millimetres (8–24 in) long and weighs 0.45–4.08 kilograms (1–9 lb) in weight, but has been known to weigh as much as 20 kg (44 lb), making this the heaviest crustacean in the world. Together with Sagmariasus verreauxi, it is also the longest decapod crustacean in the world; an average adult is about 230 mm (9 in) long and weighs 680 to 910 g (1.5 to 2 lb). The longest American lobsters have a body (excluding claws) 64 cm (25 in) long. According to Guinness World Records, the heaviest crustacean ever recorded was an American lobster caught off Nova Scotia, Canada, weighing 20.1 kg (44.4 lb).

Homarus americanus is distributed along the Atlantic coast of North America, from Labrador in the north to Cape Hatteras, North Carolina, in the south. South of New Jersey, the species is uncommon, and landings in Delaware, Maryland, Virginia and North Carolina usually make up less than 0.1% of all landings. A fossil claw assigned to Homarus americanus was found at Nantucket, dating from the Pleistocene. In 2013, an American lobster was caught at the Farallon Islands off the coast of California. It has been introduced to Norway and potentially Iceland.

The natural diet of H. americanus is relatively consistent across different habitats. It is dominated by mollusks (especially mussels, clams and snails), echinoderms and polychaetes, although a wide range of other prey items may be eaten, including other crustaceans (such as crabs), brittle stars, cnidarians and small fish. It will also feed on dead animals, as well as algae and eelgrass. Since lobsters sometimes eat their own molted shell, they were thought to be cannibalistic, but this has never been recorded in the wild. Lobsters in Maine have been shown to gain 35–55% of their calories from herring, which is used as bait for lobster traps. Only 6% of lobsters entering lobster traps to feed are caught.

The American lobster thrives in cold, shallow waters where there are many rocks and other places to hide from predators. It typically lives at a depth of 4–50 m (13–164 ft), but can be found up to 480 m (1,570 ft) below the surface.

Mating only takes place shortly after the female has molted and her exoskeleton is still soft. The female releases a pheromone which causes the males to become less aggressive and to begin courtship, which involves a courtship dance with claws closed. Eventually, the male inserts spermatophores (sperm packets) into the female's seminal receptacle using his first pleopods; the female may store the sperm for up to 15 months.