Reproduction and Life Cycle
Lobsters mate in a shelter during the summer when the female has just moulted and her carapace is still soft. The male turns the female over on her back and transfers his sperm cells into the female using his first pair of swimmerets (gonopods). After the mating is over, the male puts the female back on her legs and protects her for a few days, enough time for her carapace to harden. After mating, the female keeps the male's sperm for several months (up to one year and even more).
For most females, the eggs will be laid the year after mating. The eggs are fertilized outside the female when the eggs are laid. After they’re laid, the eggs remain attached under the tail, on the pleopods, by a kind of sticky substance. The female then keeps her tail folded up under her and carries her eggs for almost a year (between 9 and 12 months). Therefore, females mate approximately once every two years. A female can lay a few thousand eggs when she is young and several tens of thousands of eggs when she is older.
Females can lose up to 50% of their eggs during the incubation period. These losses can be caused by disease, parasites, predation, or by fishermen repeatedly catching, handling, and then releasing egg-bearing females.
When the eggs are ready for hatching, the female lifts her abdomen and thousands of lobster larvae float to the surface of the water. Temperature is a very significant element for the hatching of eggs. Larvae are released in summer when water temperatures increase. Depending on the area, hatching occurs between May and September, but most of the time it occurs in June, July and August.
Larvae are very dissimilar from adult lobsters. They resemble a tiny shrimp measuring only a few millimetres. When they hatch (stage I), larvae swim close to the surface. They are said to be planktonic. During this period, they moult twice to reach stage II, and then stage III.
The third moult is a metamorphosis. When larvae of stage III moults, they change and resemble for the first time to tiny lobsters, and are called “postlarvae”. Postlarvae measure between 11 and 14 mm. It is an important development step because this is the stage when lobsters settle on the bottom. Postlarvae swim around while quickly exploring the bottom until they find a favourable place to settle. In a natural setting, it takes between 3 and 12 weeks after hatching to reach the postlarval stage, depending on water temperature.
When postlarvae find a good habitat, they settle in a shelter on the bottom and moult quickly. It is said that lobsters become benthic.
At the beginning of their benthic life, lobsters are cryptic. They remain hidden almost all the time to protect themselves from predators. If a younger lobster must come out to feed or to find a larger shelter, it will do so at night. When their cephalothorax reaches between 15 and 25 mm in length, lobsters are emerging. Their claws are a little more developed and they come out a little more, while remaining close to their shelters. When their cephalothorax reaches between 25 and 40 mm, lobsters become vagile. They come out much further and hunt more freely. They become adolescent when their cephalothorax is over approximately 40 mm. Their reproductive organs develop, and lobsters are adult when they are able to breed. Size at maturity varies considerably according to area and gender. Maturity is generally reached at sizes larger than 60 mm. Out of 10,000 larvae at the beginning, it is estimated that approximately only one will survive until adulthood.
Lobsters must moult in order to grow, that means they must shed their carapace. The carapace of the cephalothorax splits in two, and the lobster pulls its body through first, then its claws, its legs and its tail. Once through, the lobster is as soft as gelatine. The lobster absorbs a large quantity of water to increase volume. At first, the new carapace is very flexible and not very solid. It will harden with time. Approximately a month is needed for the carapace to harden completely. After having moulted, lobsters are 15% to 20% larger than before and their weight increases approximately by 40% to 50%.
At the beginning of their benthic life, lobsters grow quickly and very often change carapace. They can moult 4 to 5 times in the first year. As adults, lobsters moult approximately once per year. When they reach a certain size, they grow slower and sometimes several years will pass before they change carapace. Before attaining their commercial size, lobsters will have moulted approximately 20 times. Generally, lobsters moult in the summer when water temperatures are warmer. Growth and moulting are greatly influenced by temperature. Lobsters moult more often and grow more rapidly when in warm water. Therefore, two lobsters of the same size can be of different ages depending on where they lived. In the Magdalen Islands, it is estimated that lobsters reach their commercial size at around 8 years of age. However, lobsters can reach their commercial size at the age of 5 in certain areas where the water is warmer. In areas where the water temperature remains cold year-round, it can take up to 10 years.
Currently, there are no techniques to determine a lobster's precise age. Every time they grow, lobsters change carapace. Therefore, there is no trace of growth on their body that can indicate their age (such as the growth rings found on the scales of fish, for example). We therefore don't know how long lobsters can live. Age is estimated according to size and growth rate based on temperature. We know however that they can live many years (at least 50) and reach very large sizes. In 1977, a lobster weighing 20 kg and measuring approximately 1 meter (overall length) was caught in Nova Scotia. Off the coast of Massachusetts in the U.S., a similar lobster was also reported (20 kg, overall length: 91 cm). Moreover, certain records document the capture of a lobster with an overall length between 1.5 and 1.8 meters.