Browsing by Subject "South coast rock lobster"

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    The 2007 Age-Structured Production Model assessments and projections for the South Coast rock lobster resource-routine update using model fitting to catch-at-age data
    (2007) Johnston, Susan J; Butterworth, Doug S
    The assessment conducted in 2006 (WG/06/06/WCRL3) has been routinely extended, taking account of a further year’s catch, CPUE and catch-at-age data. The observed CPUE shows a slight decrease for 2005 (2005/06 season). The sustainable yield estimates are generally very similar to those for the 2006 assessment, although estimates of current biomass levels relative to K increase. The Reference Case (RC) scenario suggests that a TAC of about 330 MT or less would be appropriate to prevent biomass decline in the future. The other two scenarios reported suggest higher values than this. If the catch-at-age data are down-weighted, then this 360 MT level for the TAC is increased to 390 MT.
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    South coast rock lobster OMP 2014: initial specifications
    (2014) Johnston, Susan J; Butterworth, Doug S; Glazer, Jean Patricia
    An OMP for recommending the TAC for South Coast rock lobster resource was first developed and implemented for 20081 (Johnston and Butterworth 2008). A number of further OMPs have been developed for the management of this resource. These OMPs have all had similar underlying structures, with a median target spawning biomass / of 1.20 when simulation tested. i.e. a spawning biomass increase in median terms of 20% over the 2006-2025 period. These OMPs were “slope-based” – that is the TAC-setting algorithm was based on the slope (gradient) of recent CPUE values to determine the TAC increase or decrease. The operating model which was used to simulation test OMP-2014 is model RC1 reported in Johnston (2013). The parameters of RC1 were estimated in a Bayesian framework using MCMC. The resultant posterior distribution was used to generate 1000 vectors of parameters and current numbers at age to commence projections which were used to test candidate MPs. The median, 5th and 95th percentiles for all performance statistics were produced. OMP-2014 as described below is to be used for setting the TACs for the South Coast rock lobster fishery for four seasons (2014-2017), and will be subject to review and possible revision in 2018. Furthermore this document (including its Appendix) contains only the initial specifications of OMP-2014, as these will be extended in the near future, following further simulation testing, to allow for “Exceptional Circumstances”, and in particular to provide a specific metarule governing the process under which the 5% maximum TAC inter-annual reduction constraint would be over-ruled if CPUE drops below a threshold level still to be determined. 2.