Browsing by Subject "South Coast rock lobster resource"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- ItemRestrictedThe 2007 age-structured production model assessments and projections for the South Coast rock lobster resource-routine update using Pope's approximation model fitting to catch-at-age data including scenarios for time-varying selectivity(2007) Johnston, Susan J; Butterworth, Doug SThe assessment conducted in 2006 (WG/06/06/WCRL3) has been routinely extended (except that the Baranov equation has been replaced by Pope’s approximation), taking account of a further year’s catch, CPUE and catch-at-age data.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 a little less than 330 MT or less would be appropriate to prevent biomass decline in the future. The other four scenarios reported suggest higher values than this, ranging from 350 MT to 405 MT. Spawning biomass trends over the last 10 years are downward for all the models considered.
- ItemOpen AccessFinal set of OMP results for the South Coast rock lobster resource OMP(2008) Johnston, Susan J; Butterworth, Doug SResults are presented here for a range of OMP tunings which assume/attain either i) inter-annual TAC constraint of 5%, 7.5% or 10% ii) median recovery levels sp B (2025/2006) of either 1.10, 1.175 or 1.25. The five OMP candidates presented are: OMP1 10% inter-annual TAC constraint + median 1.10 sp B (2025/2006) OMP2 10% inter-annual TAC constraint + median 1.24 sp B (2025/2006) OMP3 7.5% inter-annual TAC constraint + median 1.18 sp B (2025/2006) OMP4 5% inter-annual TAC constraint + median 1.10 sp B (2025/2006) OMP5 5% inter-annual TAC constraint + median 1.25 sp B (2025/2006)
- ItemOpen AccessInitial OMP results for the South Coast rock lobster resource OMP(2008) Johnston, Susan J; Butterworth, Doug SSome initial results following the development of an OMP framework for the management of South Coast rock lobster are presented here, corresponding to a constant catch scenario and runs of a CPUE-tuned-based feedback control rule. First though, the assumptions made for the OMP testing are listed below. Assumptions required for future projections for OMP testing Summary of current assessments (note 2005 refers to the 2005/6 season): • Fit to CPUE and CAL data up to and including 2005 • The assessment includes observed catches for 2006; thus the assessment ended at the start of 2007 i.e. projections start at beginning of 2007 • However the 2007 catch is now known • The OMP thus needs to sets its first OMP TAC for 2008 • The OMP will use model-generated CPUE from 2006 • The OMP TAC for year y will use CPUE data from 1974 - (y-2), and catches from 1973 to (y-1). In programming terms, the population projection commences at the start of 2006, though with fixed catches until these are first set by the OMP in 2008. When projecting the population forwards for the simulation testing of various OMP candidates, a number of assumptions need to be made for the operating models to be used.
- ItemOpen AccessNear final specifications for the sex- and area-specific Operating Models for testing OMPs for the South Coast rock lobster resource(2008) Johnston, Susan J; Butterworth, Doug SThis document reports results of nine different models for the assessment of the South Coast rock lobster resource and associated fishery at an area-specific level. It is proposed that from these nine models, a smaller set will be selected to form a “Reference Set” to be used as operating models for the testing of alternate management procedures, with the remainder serving as operating models for robustness tests.. One of the main new aspects of these results is the use of the “new” historic catch series which allocates overcatch on the basis of the areal distribution of catches by Hout Bay Fishing; more the details about this are to be found in Glazer and Butterworth (2008a).
- ItemOpen AccessOMP 2008 for South Coast rock lobster resource(2008) Johnston, Susan J; Butterworth, Doug S; Glazer, Jean PatriciaOMP 2008 consists of an algorithm that calculates the TAC for the resource using CPUE data collected from each of three areas (New Areas 1, 2 and 3 – see Fig. 1), Note that the TAC for season y+1 will be based upon the CPUE series that ends in season y-1, i.e. the TAC recommendation for 20081 would be based on a CPUE series that ended with the most recent CPUE value available at the time a recommendation was requested which would be for 2006.
- ItemOpen AccessRecommended TAC 2008 from the new OMP for the South Coast rock lobster resource(2008) Johnston, Susan J; Butterworth, Doug SJohnston and Butterworth (2008) reports expected results for the final OMP 2008 for the South Coast Rock Lobster fishery. This OMP 1. has a 5% maximum TAC change constraint, and 2. has a median anticipated sp B (2025/2006) of 1.20 under operating Model 3 (MARAM TVS).
- ItemOpen AccessResults for the final OMP 2008 selected for the South Coast rock lobster resource(2008) Johnston, Susan J; Butterworth, Doug SIn Johnston and Butterworth (2008) results for a range of OMPs for the South Coast rock lobster fishery were reported. These OMPs varied with respect to the maximum extent of inter-annual TAC variability allowed (5%, 7.5% or 10%) as well as the median spawning biomass recovery anticipated over the next 20 years ( sp B (2025/2006) - ranges from 1.10 to 1.25 were presented). The South Coast rock lobster SWG had previously decided that the preferred OMP should be intermediate to the OMP 4 and OMP 5 presented in Johnston and Butterworth (2008) which would: 1. have a 5% maximum TAC change constraint, and 2. have a median anticipated sp B (2025/2006) of 1.20 under operating Model 3 (MARAM TVS).