Contrasting sizes at sexual maturity of southern rock lobsters (Jasus edwardsii) in the two Victorian fishing zones: implications for total egg production and management

Abstract

Fecundity (F) of Jasus edwardsii Hutton (Decapoda:Palinuridae) in the two Victorian fishing zones (Eastern and Western) was estimated from egg masses collected from 98 mature females (97–164 mm carapace length, CL) and was found to be related to carapace length (CL) by the equation F = 0·0316L^3.359 (r² = 0·8539; n = 571). Size at onset of sexual maturity (SOM), estimated from samples of the commercial catch (n = 3891) and analysed to determine the smallest size class in which 50% of females were carrying eggs or possessed ovigerous setae, was lower in the Western Zone (90 mm CL) than in the Eastern Zone (112 mm CL). Fecundity and SOM estimates and length frequencies in the commercial catch were used to estimate the relative reproductive potential (RRP) of each 5-mm-CL size class. The maximum RRP in the Western Zone was attributed to the size classes of 105 (38%) and 110 mm CL (25%), whereas the maximum RRP in the Eastern Zone was attributed to the size classes between 130 (40%) and 135 mm CL (16%). This study indicates that the current minimum legal size limits need to be reassessed and that separate management strategies for the two zones need to be considered.