Browsing by Subject "OMP"

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    A history of recent bases for management and the development of a species-combined Operational Management Procedure for the South African hake resource
    (National Inquiry Services Centre, 2010) Rademeyer, Rebecca A; Plagányi, Éva E; Butterworth, Doug S
    The bases for historical catch limits placed on the hake fishery are reviewed in brief for earlier years and then in some depth over the period from 1991 when the Operational Management Procedure (OMP) approach was introduced for this fishery. The new OMP implemented from 2007 was the first to be based on the use of rigorous species-disaggregated assessments of the resource as Operating Models. The paper describes the Reference Set and range of robustness trials, together with the associated Operating Models, which were used for the simulation testing of the new OMP. Performance statistics for a number of candidate OMPs are compared, and the two key trade-off decisions in the selection process discussed (substantial Merluccius paradoxus and catch per unit effort [CPUE] recovery, and total allowable catch [TAC] stability constraints). Details of the OMP adopted and how its formulae depend on recent trends in CPUE and survey estimates of abundance are provided. OMP-2007, which is tuned to a median 20-year recovery target of 20% of pristine spawning biomass for M. paradoxus and a 50% increase in CPUE over the next 10 years, has been adopted for recommending hake TACs over the 2007–2010 period until the next scheduled major review. A set of general guidelines adopted for the process of possible overruling of recommendations from OMPs or bringing forward their reviews within an otherwise intended four-year cycle is detailed.
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    Implications to existing OMP of the 2010 updated assessments of the south coast rock lobster resource
    (2010) Johnston, Susan J; Butterworth, Doug S
    Johnston and Butterworth (2008) reported 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). Recently, a programming glitch in the operating models has been discovered. The result of correcting this glitch is reported in Johnston and Butterworth (2010). Here we compare the OMP 2008 expected performance statistics using the original 2008 operating models with those produced using the corrected operating models conditioned on the data available at that time. The current “OMP 2008” was tuned using the original 2008 Model 3 operating model.
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    Initial OMP results for the South Coast rock lobster resource OMP
    (2008) Johnston, Susan J; Butterworth, Doug S
    Some 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.
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    Near 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 S
    This 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).
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    The new West Coast rock lobster OMP based on an area-disaggregated approach
    (2007) Johnston, Susan J; Butterworth, Doug S
    The OMP currently being developed for the West Coast Rock Lobster is different from the three previous OMPs applied to manage the resource (see Johnston and Butterworth 2005), in that this new OMP will provide TACs for each of the five super-areas on an annual basis. During 2006, considerable work was focussed on the development of assessment models for each super-area. These assessment models now form the “operating models” which are used for testing alternate OMP candidates and are described in ANSW/JUL07/WCRL/ASS/1 and 2. The new OMP uses data (trap and hoop CPUE, FIMS, somatic growth rate) from each area (where available), combines these data into a single index (for each data type), produces a global TAC, and then uses a series of rules to split this global TAC into TACs at the super-area level. At the same time, estimates of recreational catch for each super-area are taken into account, as well as ensuring that super-area TACs will allow the allocations to the limited rights holders (smaller scale operators restricted to a particular super-area) to be taken each year.
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    OMP 2007 re-cast to be used for setting TACs for the West Coast rock lobster fishery for the 2008+ seasons
    (2010) Johnston, Susan J; Butterworth, Doug S; Glazer, Jean Patricia
    This document first gives the reasons why the OMP agreed for West Coast rock lobster in 2007 (OMP-2007) was “re-cast” the following year, listing the modifications then introduced. It then provides details of the three main components of “OMP-2007 re-cast”: 1) how data are combined across the five super-areas (Area 1-2, Area 3-4, Area 5-6, Area 7 and Area 8) for input into the OMP; 2) the OMP formulae which provide the global TAC recommendation; and 3) the manner in which the global TAC is split amongst super-areas and resource usergroups
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    OMP-2011 re-tuned to account for 2012/13 TAC decisions while maintaining an unchanged recovery target
    (2013) Johnston, Susan J; Butterworth, Doug S
    The consequences of retuning OMP-2011 to achieve the agreed 35% median recovery level by 2021 given the decision not to decrease the 2012/13 season TAC by 150 tons as recommended are investigated. Over the next eight seasons, the aggregate TAC is forecast to be some 400 tons less than would otherwise have been the case. Most of the reduction will be borne by the offshore commercial sector, which should expect a reduction near the maximum 10% constraint over each of the next three seasons, and an allocation eventually stabilising about 100 tons (or some 7%) than would otherwise have occurred. The probability over the next two years of Exceptional Circumstances needing to be declared in super-area A7, with a consequent additional TAC reduction, roughly doubles. Certain other possible management approaches which explicitly exclude the possibility of future TAC reductions, are shown to run the risk of an appreciably larger biomass reduction by 2021.
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    Recommended TAC 2008 from the new OMP for the South Coast rock lobster resource
    (2008) Johnston, Susan J; Butterworth, Doug S
    Johnston 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).
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    Results for the new West Coast rock lobster OMP
    (2007) Johnston, Susan J; Butterworth, Doug S
    The results presented here are for the current “best-performing” OMP. Results included using the “observed” 2005 somatic growth data provided by James Gaylard (OLRAC). (Note: 2005 refers to the 2005/06 season.) The OMPs presented here are meant to be tuned so that the average commercial TAC over the 10-year period is either 2000 MT, 2200 MT, 2400 MT or 2600 MT. Due to lack of time, the current tuning is approximate with these values actually being 2030 MT, 2245 MT and 2401 MT and 2596 MT. The OMP presented assumes that 5% of the A8 commercial TAC is transferred to super-areas A34 and A7 with a ratio of 0.20:0.80 respectively. The rationale behind this selection of TAC transfer is to attempt to get a more even spread of resource depletion/recovery across all five super-areas.
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    Updated performance statistics for the existing OMP and modified tunings thereof for the west coast rock lobster resource
    (2005) Johnston, Susan J; Butterworth, Doug S
    Performance statistics for the current OMP, as adopted in 2003, are recomputed using an operating model that incorporates a reassessment including data that have become available since that time. The OMP is retuned to give the same median biomass increase target over 2003 to 2013 as was the case for the 2003 analyses. The same OMP approach is applied to data and assessments for super-area Area 8.