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 = 0·0316L3.359 (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.

Spatial variation in size at onset of maturity of female southern rock lobster <i>Jasus edwardsii</i> around Tasmania, Australia

“…Jasus edwardsii are fished to the north of the Tasmanian region examined here but SOM does not continue to increase, which demonstrates that the linear model of SOM described here cannot be extrapolated beyond our data series. SOM for populations off western Victoria that are influenced by upwellings of cold, nutrient-rich water was estimated at 90 mm CL, while SOM for populations off eastern Victoria was estimated at 110 mm CL (Hobday and Ryan, 1997). The spatial pattern observed around Tasmania in SOM was equivalent to that described for growth of J. edwardsii around Tasmania by , which is consistent with the hypothesis that SOM in female lobsters is age-specific rather than size-specific (Pollock and Goosen, 1991).…”

Does pleopod setation provide a measure of maturity in female southern rock lobsters <i>Jasus edwardsii</i>?

“…Size at onset of maturity in Jasus species is most often based on observations of the endopodite of pleopods-where ovigerous setae are well developed the animals are classed as mature (e.g. Booth, 1984;Cockcroft and Goosen, 1995;Hobday and Ryan, 1997). This measure of maturity is related to the need for setae for egg attachment after extrusion, so there is an expectation that females without setose endopodites would be unable to successfully brood eggs.…”

“…The classification of female lobsters as mature can be made on the basis of several characters, including ovarian development, the presence of external eggs, endopodite processes of pleopods bearing ovigerous setae, sperm within seminal receptacles or spermatophore (tar spot), and the morphometry of the abdomen, legs or pleopod exopodite (Krouse, 1973;Plaut, 1993;Hobday and Ryan, 1997;Minagawa and Sano, 1997). Size at onset of maturity in Jasus species is most often based on observations of the endopodite of pleopods-where ovigerous setae are well developed the animals are classed as mature (e.g.…”

“…1992; Hobday and Ryan, 1997). SOM estimates were based on the presence of ovigerous setae while SOB estimates were based on the presence of external eggs during the brooding period.…”

The Effect of Cooking on Carapace Length of Southern Rock Lobster, Jasus Edwardsii (Hutton, 1875) (Decapoda, Palinuridae)

“…The species supports valuable commercial and recreational fisheries across the whole of its range, which covers several management jurisdictions. One consistent management tool is the use of a minimum legal size based on carapace length (CL), although actual size limits differ between states (Frusher et al, 1997;Hobday & Ryan, 1997;McGarvey et al, 1997) .…”