Size at onset of maturity
The size at onset of maturity for female rock lobsters, J. edwardsii, has been defined as the size or size class at which 50% of the rock lobsters in a sample are mature. Animals are regarded as mature if they are bearing external eggs attached to the pleopods or if there are well developed setae on the endopodites of the pleopods.
Immature females usually moult twice a year until maturity, then annually. Where size at 50% maturity is large, some females may begin moulting once a year before maturity.
The size at which 50% of females are mature varies considerably for J. edwardsii throughout New Zealand, from 72 mm Carapace Length (CL) near Gisborne to 121 mm CL in eastern Foveaux Strait. This size appears inversely related to water temperature. No data are available from the Chatham Islands.
Size at 50% female maturity in most areas is less than the minimum legal size of 60 mm tail width (TW) (approximately 93 – 98 mm CL). Most females from these areas breed at least once before reaching the minimum legal size. However, from Banks Peninsula through western Foveaux Strait (CRA7 and part of CRA8), size at 50% maturity is greater than the minimum legal size. The effects of this are not known, but these areas have sustained high catches over time.