When the female releases her eggs, she uses the small claws on her last pair of walking legs to open the spermatophore and fertilize the eggs. Fertilized eggs are attached to the underside of the female’s tail primarily in May and June. Egg carrying females generally inhabit water less than 30 ft deep and carry their eggs for about 10 weeks, with larger females producing more eggs. A small female might carry about 120,000 eggs, while a large female might carry 680,000 eggs.
Spiny lobster eggs hatch into tiny, transparent larvae with flattened bodies and spider-like legs. They drift with the prevailing currents, feeding on other tiny animals. They may drift 400km offshore, and are found from the surface to a depth of over 150m.
As with many crustaceans, spiny lobsters must shed their outer shell to grow. This process, known as “molting”, is preceded by the formation of a new, soft shell under the old one. Lobsters take in water to expand the new shell before it hardens. They are more vulnerable to predation and physical damage right after they molt, until their shell becomes hard.