Among the largest crustaceans, lobsters stand out for their potential to grow far beyond the typical dinner-plate size. While most commercially caught lobsters weigh only a few pounds, the species that inhabit the North Atlantic can reach impressive dimensions. These massive specimens highlight a unique biological process that allows these animals to continue increasing in mass for decades.
The Official World Record Holder
The title for the largest lobster ever officially recorded belongs to an American lobster (Homarus americanus), caught off the coast of Nova Scotia, Canada, in 1977. This lobster weighed 44 pounds and 6 ounces, securing its place as the heaviest marine crustacean ever documented. It measured three feet and six inches from the tip of its largest claw to the end of its tail fan.
The record-holding lobster inhabited the cold, deep waters of the North Atlantic. Based on known growth rates, this immense size suggests the lobster was well over 100 years old when caught. The 1977 Nova Scotia catch remains the acknowledged benchmark for weight and dimension, despite unverified claims of larger lobsters.
The Science of Giant Lobster Growth
A lobster’s ability to achieve massive size is linked to its unique growth mechanism, known as ecdysis, or molting. Since a lobster is encased in a rigid exoskeleton, it must periodically shed this hard shell to increase its body size. A new, soft shell forms underneath, and the lobster absorbs water to expand its body before the new shell hardens.
Young lobsters molt frequently, sometimes up to 25 times in their first five to seven years, but the frequency decreases dramatically with age. Adult lobsters may only molt once every year or two. Each successful molt results in a significant size increase, adding approximately 15% to their length and up to 40% to their weight. This indefinite growth, combined with extreme longevity, allows rare individuals to become true giants.
As a lobster ages, the energy required for molting becomes substantial, and the risk of complications increases. Older lobsters may skip their annual molt, leading to a worn, scarred, and weakened shell. Most succumb to disease or predation before reaching the enormous sizes of the record holders.
Comparing the Largest Lobster Species
The American lobster (Homarus americanus) is the heaviest crustacean species in the world, possessing a greater size potential than its relatives. Its large, heavy claws contribute significantly to its overall weight, making it the most likely candidate for mass records. The European lobster (Homarus gammarus) is closely related but generally smaller. The largest recorded European specimen was caught in 1931 off Cornwall, England, weighing 20 pounds and 8 ounces (9.3 kilograms).
Spiny lobsters (Family Palinuridae) have a different body structure and rarely compete with the Homarus species in weight. They lack the massive, crushing claws characteristic of American and European lobsters, instead possessing long, thick, spiny antennae. The largest California spiny lobster (Panulirus interruptus) on record weighed 16 pounds and 1 ounce, confirming that the clawed lobsters of the North Atlantic hold the size distinction.