Browsing by Subject "operating models"

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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 West Coast rock lobster operating models for super-areas A1+2 and A8+
    (2011) Johnston, Susan J; Butterworth, Doug S
    At the previous SWG meeting (23 March 2011) results of updated operating models for all five super-areas of the west coast rock lobster resource were presented (Johnston and Butterworth 2011). The SWG requested that two of the operating models be re-run following discussions at the meeting. These re-runs are: Area 1+2: Re-run the model with the constraint that all estimable recruitment parameters must be 1.0, when expressed as a proportion of the pristine recruitment. Area 8+: Re-run the model with updated values for both the trapboat and hoopnet CPUE series. Glazer and Butterworth (2011a,b) report updated CPUE values. These values have been updated to include Area 8 sub-areas and to take into account Areas 10-14 as recommended.
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    Reference observations for validating and tuning operating models for krill fishery management in area 48
    (2008) Hill, Simeon; Hinke, Jefferson; Plagányi, Eva; Watters, George
    In 2007 WG-SAM defined a set of reference observations for validating and tuning proposed models to evaluate krill catch allocation options for Area 48 (the SAM calendar). The observations, which were endorsed by WG-EMM, were largely qualitative and relative. We used available data to translate these observations into numerical terms (the numerical calendar). We provide spatially-resolved reference points for the density of krill, and the abundance of “generic” seals, penguins and whales in 1970, 2007 and at least one intermediate year. Recent work on baleen whales indicates a higher growth rate than that suggested by WG-SAM, so the numerical calendar for this taxon deviates from the SAM calendar. The numerical calendar is a partly subjective interpretation of limited data and should not be considered a definitive description of the relevant dynamics. This exercise resulted in population sizes for several taxa that are adjusted for asynchronous observations and are potentially more suitable for initialising models than those published in Hill et al (2007).
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    Updated West Coast rock lobster operating models
    (2011) Johnston, Susan J; Butterworth, Doug S
    A number of recommendations pertaining to the assessment of West Coast rock lobster were made by the panel at the international workshop held in Dec 2010. The authors have taken these into account and updated all five operating models for the West Coast rock lobster resource. The following are items that have been checked and modified in the operating models and associated input data.