Typical male lobsters will deposit packets of sperm on the underside of the female. The female will later use the sperm to externally fertilize her eggs as they are laid. The female can store the sperm for several months, waiting for the egg-laying season, which typically occurs during July and August. Females breed every two years.
Female lobsters carry their eggs (known as berries) beneath their abdomen, attached to structures called spinnerets. The number of eggs is related to the size of the female, and is typically about 5,000 eggs for a 10 in (25 cm) long female, and 40,000 for a 14 in (36 cm) long animal. However, one 17 in (43 cm) long female had 63,000 eggs, and another slightly larger one had 97,000.
The egg masses are periodically waved on their spinnerets to ensure their access to clean, well-oxygenated water. Female lobsters carry their eggs for 10-11 months. Hatchling lobsters are planktonic and commonly disperse quite widely with water currents. After their fifth molt, when they are about 1 in (2.5 cm) long, the young lobsters go to the bottom and begin the relatively sedentary existence that they have for the rest of their lives. Lobsters are extremely vulnerable to the vagaries of drift and predation when they are in their planktonic stage, and when they are benthic but small. This is the reason for the enormous reproductive output of these animals.