Browsing by Subject "south coast rock lobster"

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    The Age-Structured Production Model for the south coast rock lobster population
    (2005) Johnston, Susan J; Butterworth, Doug S
    The south coast rock lobster resource is modelled using an age-structured-productionmodel (ASPM).
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    Final 2010 operating models for south coast rock lobster assessment update
    (2010) Johnston, Susan J; Butterworth, Doug S
    This document reports assessment results for the five final 2010 operating models (OMs) used to update the South Coast rock lobster resource assessments. These OMs contain the following modifications from the versions reported in Fisheries/2010/JUL/SWGSCRL/08: • Somatic growth parameters estimated during fitting procedure to be used for all length-at-weight relationships. • Mean of recruit residuals over 1974-2000 period forced to zero. The five OMs are: 1. Model 3 (MARAM time-varying selectivity) 2. Model 4 (OLRAC time-varying selectivity) 3. Effort Saturation (Model 3 but with effort saturation included – see Appendix for methodology) 4. CAL-down-weight (Model 3 but catch-at-length data down-weighted by a multiplicative factor of 0.1) 5. Fix h=0.8 (Model 3 but with stock recruitment steepness parameter h fixed at 0.8).
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    Further updated south coast rock lobster stock assessments for 2010 and comparisons to the 2008 and 2009 assessments
    (2010) Johnston, Susan J; Butterworth, Doug S
    This document is submitted in response to the requirement that “simple routine updated assessments (likely no more than core reference set models used in the OMP testing refitted taking a further year’s data into account)” be tabled every year an OMP is in operation for a fishery (MCM, 2007) This document reports such updated stock assessments for the South Coast rock lobster fishery. Essentially three further years’ CPUE and catch-at-length data are available since the assessments upon which OMP testing was based were carried out in 2008 (see Johnston and Butterworth 2008a). Assessment updates produced in 2009 are now able to be further updated with one years’ data. Although Johnston and Butterworth (2008a) initially presented stock assessment results for a wide range of models, only Models 3 and 4 were used as a final Reference Set in final OMP deliberations.
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    Updated south coast rock lobster stock assessments for 2009
    (2009) Johnston, Susan J; Butterworth, Doug S
    This document is submitted in response to the requirement that “simple routine updated assessments (likely no more than core reference set models used in the OMP testing refitted taking a further year’s data into account)” be tabled every year an OMP is in operation for a fishery (MCM, 2007) This document reports such updated stock assessments for the South Coast rock lobster fishery. Essentially two further years’ CPUE and catch-at-length data are available since the assessments upon which OMP testing was based were carried out in 2008 (see Johnston and Butterworth 2008a). Although Johnston and Butterworth (2008a) initially presented stock assessment results for a wide range of models, only Models 3 and 4 were used as a final Reference Set in final OMP deliberations. Updates of Models 3 and 4 are thus presented here. To recap: Model 3 – assumes time-varying selectivity using the MARAM method Model 4 – assumes time-varying selectivity using the OLRAC method. Besides data updates, a further update to these assessment models is that the period for which recruitment residuals are estimated is extended from 1974-1997 by two further seasons to 1974-1999.