Growth rates of juvenile southern rock lobster (Jasus edwardsii ) estimated through a diver-based tag ] recapture program Adrian Linnane A,D , David Hobday B , Stewart Frusher C and Caleb Gardner C A South Australian Research and Development Institute (Aquatic Sciences), PO Box 120, Henley Beach, SA 5022, Australia. B Fisheries Research Branch, Department of Primary Industries, PO Box 114, Queenscliff, Vic. 3225, Australia. C University of Tasmania, Institute of Marine and Antarctic Studies, Private Bag 49, Hobart, Tas. 7001, Australia. D Corresponding author. Email: Adrian.Linnane@sa.gov.au Abstract. Despite being one of the most economically important fisheries in south-eastern Australia, growth rates of juvenile southern rock lobster (Jasus edwardsii) have not previously been quantified in the wild. This study utilised a diver-based tag–recapture program to estimate growth rates of individuals between 40–80 mm carapace length (CL) in temperate reef sites across south-eastern Australia. Of the 7064 lobsters tagged and released, 978 (14%) were recaptured with recapture rates of 23, 5 and 7% in the States of Tasmania, South Australia and Victoria respectively. Although individual growth increments were similar between the sexes, differences in annual growth rates were evident at 50 mm CL, with males growing ,1.4 times faster than females. Increased levels of growth in males resulted from a higher moult frequency, which was found to significantly reduce in females as they reached sexual maturity at ,70–80 mm CL. No significant difference was found in growth rates of males or females between the States when all sites within each State were combined. The growth estimates from this work contribute to the understanding of juvenile lobster population dynamics and will improve current fishery models by confirming relationships between early juvenile, pre-recruit abundance and entry to the fishable biomass. Received 3 June 2011, accepted 8 October 2011, published online 28 November 2011 Introduction Given the economic importance of lobster fisheries, growth rates of several species have been highly profiled worldwide. Research to date on palinurid lobsters has largely focussed on late-juvenile and adult life history stages whereas estimates for post settlement to late juveniles are less numerous. This primarily relates to the behavioural characteristics of these species combined with size-selectivity effects from commercial fishing gear on which many recapture studies depend. Early juvenile (,35 mm carapace length; CL) palinuridae are asocial and dwell solitarily in vegetation or isolated holes with reef habitat (Butler and Herrnkind 1991; Edmunds 1995). At around 35–40 mm CL, juveniles undergo ontogenetic changes in sociality that alters their aggregation patterns and use of shelters (Ratchford and Eggleston 1998; Butler et al. 1999). Driven by chemical cues released by conspecifics (Ratchford and Eggleston 1998), juveniles start to congregate in crevice shelters. However, even as larger crevice-dwelling juveniles, movement away from shelters appears limited (,25 m), only increasing as individuals reach the pre-recruit and adult stages (MacDiarmid et al. 1991). As a result, juvenile lobsters are less likely to come into contact with commercial pots during routine fishing operations. In addition to behavioural characteristics, commercial fishing gear is now designed to minimise catches of undersized lobsters, with escape gaps compulsory in many fisheries worldwide. Mandatory mesh sizes are also enforced with the aim of releasing juvenile lobsters before hauling. Consequently, the combination of behavioural traits and commercial pot design mean that smaller-sized juveniles are rarely seen in fisheries where pots as used as a method of capture. In Australia, the palinurid southern rock lobster (Jasus edwardsii) supports important commercial and recrea- tional fisheries across the south-eastern States of South Australia, Victoria and Tasmania with a combined catch of ,3000 tonnes annually (Linnane et al. 2010). Fishing methods have generally remained unchanged over time, consisting of baited pots that are set individually overnight and hauled at first light. Previous tagging studies in the fisheries (Punt and Kennedy 1997; McGarvey et al. 1999) have relied on commer- cial pots as a method of capture and, as a result, provided growth estimates for pre-recruit and adult individuals only. CSIRO PUBLISHING Marine and Freshwater Research http://dx.doi.org/10.1071/MF11121 Journal compilation Ó CSIRO 2011 www.publish.csiro.au/journals/mfr