© 2006 International Council for the Exploration of the Sea
Interannual variation in the moult cycle and size at double breeding of mature female western rock lobster (Panulirus cygnus)
Western Australian Fisheries and Marine Research Laboratories North Beach, Western Australia, Australia
*Correspondence to S. de Lestang: tel: +61 08 9203 0174; fax: +61 08 9203 0199. e-mail: slestang{at}fish.wa.gov.au.
The moult cycle of mature female Panulirus cygnus was examined from data recorded over 32 years at four sites along the coast of Western Australia. A repeating trend for mature females was inferred from samples taken between 15 November and 15 August. Setae were present on the endopodites of all large females from June until February–March; between March and June the proportions of females with setae declined sharply as about 80% moulted into a non-setose phase. Females that did not undergo this moult in February remained setose throughout the "normal" non-setose period before moulting and producing a new set of setae by midwinter. New or eroded spermatophores were present on most large females between November and January, but their presence declined sharply during the February–March moult, to be absent by May. The percentage of mature females that bypassed the non-setose moult varied markedly from 1% to 40%, and was well correlated with mean water temperatures in January and February. The proportion that did not undergo a moult increased when these months were cool but decreased when they were warm. The size (carapace width) at which females carry two batches of eggs in one breeding season (double breeder) declined progressively from 96.6 mm to 84.1 mm with decreasing latitude (32°S to 28°S), and further declined at the offshore Abrolhos Islands (29°S) to 78.7 mm. The implications of these findings are discussed in relation to management measures designed to protect females in a setose condition.
Keywords: double breeding, moult cycle, Panulirus cygnus, water temperature
Received 28 November 2005; accepted 6 June 2006.