1 Estimating the duration of the pelagic phyllosoma phase of the southern rock 1 lobster, Jasus edwardsii (Hutton). 2 Short Title: Duration of phyllosoma phase: J. edwardsii 3 R. W. Bradford, D. Griffin and B. D. Bruce 4 CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, Tasmania 7001 5 email: Russ.Bradford@ csiro.au 6 Note: This is the “accepted for publication” version. The final published version 7 (doi:10.1071/MF14065) in Marine and Freshwater Research differs slightly and 8 should be used for citation. 9 Abstract 10 The phyllosoma larva of the southern rock lobster, Jasus edwardsii, is thought to be 11 amongst the longest larval phases of any planktonic larva, with estimates in the 12 literature ranging from 12 to 24 months. In the present study we have used an 13 extensive archive of samples (over 2800 samples with 680 phyllosoma) to refine the 14 estimate of the duration of the pelagic phase. The distribution through the year of 15 larval stages suggested that larvae from two separate spawning events were present in 16 any 12 month period. Using regression analysis we have estimated the duration of the 17 phyllosoma phase to be 547  47.5 days (roughly 18.2  1.6 months). A new model of 18 J. edwardsii phyllosoma development is presented and compared with data on known 19 hatching and settlement patterns. The new model will improve the paramiterisation of 20 stage-specific biophysical models of larval dispersal and regional connectivity to 21 better inform management of the southern rock lobster fisheries. 22 Key Words: rock lobster, phyllosoma, Jasus edwardsii, age, larval duration 23 INTRODUCTION 24 The southern rock lobster, Jasus edwardsii, forms the basis of one of the most 25 lucrative fisheries in south-eastern Australia. In 2010-11 the value of the commercial 26 fishery was estimated to be AU$177 million, split between three States (South 27 Australia AU$96M, Victoria AU$18M, Tasmania AU$63M) (ABARES 2013). 28