Mating and eggs
At sexual maturity the female lobster’s pleopods increase in size and the inner branch grows a fringe of pale hairs to which the eggs attach after mating. The males mature at about the same size but there are no obvious external changes.
The mating season
Female lobsters can only mate when the carapace is soft (i.e. within a few weeks of moulting). Red rock lobsters moult as early as late February in southern waters, but not until late June in warmer northern waters. They can mate between 2 hours to 63 days after moulting.
Females carrying eggs occur in greatest numbers from April to October, though a few are found during any month of the year. Females bear eggs only once each year and most mature females carry eggs during the egg-bearing season.
Lobsters are selective about mates; large males prefer to mate with large females and females also prefer the largest male available. Successful reproduction requires mature male and female lobsters of similar size.
Large males become aggressive during the mating season, which usually results in one male per den. Females are also less likely to shelter together during mating when they are competing for the large males.
Once a mate has been selected the lobsters begin courtship which may last just a few minutes or several days. When they are ready to mate they rear up, belly to belly and embrace before toppling over with the female uppermost. The male then deposits a sperm package (or spermatophore) onto the belly of the female.
The sperm package begins to disintegrate immediately, so the female rapidly starts to extrude her eggs. Normally she will cling to a rock face head up and form a brood chamber with her tail, spreading the tail fans to cover the genital pores and the sperm mass. Eggs are extruded from the genital pores and fertilised as they pass through the sperm package before attaching to the long hairs on the pleopods, under the tail.
The number of eggs carried by J. edwardsii depends on size, ranging from about 125,000 for a female of 95 mm carapace length (CL) to about 540,000 for one of 170 mm CL.
Most mature female S. verreauxi moult between July and November, bear eggs during late September to January, and hatch the eggs from December to January. The number of eggs carried by S. verreauxi ranges from about 375,000 for a female of 152 mm CL to 2,000,000 for one of 230 mm CL.