Changes between Version 3 and Version 4 of EwEugUsingEcosimToStudyCompensationInRecruitmentRelationships


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Timestamp:
2010-01-30 20:13:04 (10 years ago)
Author:
varunr
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  • EwEugUsingEcosimToStudyCompensationInRecruitmentRelationships

    v3 v4  
    1111Compensatory effects can be increased (the recruitment relationship is flat over a wider range of adult stock sizes, with a steeper slope of recruitment curve near the origin) by: 
    1212 
    13 1. Limiting the availability of prey to juveniles (forcing juveniles to use small ‘foraging arenas’ for feeding) by setting all elements of the Ecosim [[Vulnerabilities flow control.htm|Vulnerabilities]] form column for the juveniles to a small value (1.5-5); or 
     131. Limiting the availability of prey to juveniles (forcing juveniles to use small ‘foraging arenas’ for feeding) by setting all elements of the Ecosim [wiki:VulnerabilitiesFlowControl Vulnerabilities] form column for the juveniles to a small value (1.5-5); or 
    1414 
    15152. Setting a higher value for the juvenile group’s ‘Feeding time adjustment rate’ parameter on the Ecosim ''Group info'' form, which causes the effective time exposed to predation while feeding to drop directly with decreasing juvenile abundance (i.e., simulates the possibility that when juveniles are less abundant, remaining ones may be able to forage ‘safely’ only in refuge sites without exposing themselves to predation risk).  This option should be used only if you are fairly sure from field natural history observation that the juveniles do in fact restrict their distribution to safe habitats when at very low abundance. 
     
    1717It is especially important to test alternative values for the vulnerability of prey to juveniles (point i).  If vulnerability is too high, the Ecosim emergent stock-recruitment relationship is likely to look almost like a straight line out of the origin, i.e. without compensatory effect.  If vulnerability is too low, the relationship may develop a ‘spurious’ dome-shape. 
    1818 
    19 Note that in Ecosim multi-stanza groups, the ‘Adult’ group is always the oldest stanza. The stock-recruitment relationship between this adult stage and each of the younger stages separately is calculated using the [[Stock recruitment S R plot.htm|Stock recruitment]] (S/R plot) form. 
     19Note that in Ecosim multi-stanza groups, the ‘Adult’ group is always the oldest stanza. The stock-recruitment relationship between this adult stage and each of the younger stages separately is calculated using the [wiki:StockRecruitmentSrPlot Stock recruitment] (S/R plot) form. 
    2020 
    2121=== A stock-recruitment exercise in Ecosim === 
    22 Always check the stock-recruitment curve shape, and play with [[Group info.htm|Group info]] and Stage parameters that may affect it, before proceeding to other policy analysis. The simplest way to check this shape while minimizing complicating and confounding effects of trophic interactions is to set up Ecosim for a fairly long time scenario (40+ yrs): 
     22Always check the stock-recruitment curve shape, and play with [wiki:GroupInfo Group info] and Stage parameters that may affect it, before proceeding to other policy analysis. The simplest way to check this shape while minimizing complicating and confounding effects of trophic interactions is to set up Ecosim for a fairly long time scenario (40+ yrs): 
    2323 
    24  1. Go to the [[Run ecosim.htm|Run Ecosim]] form (Time dynamic (Ecosim) > Output > Run Ecosim), select ''Groups'' from the drop-down ''Target'' menu on and then the adult pool. Using the fishing rate sketch pad, set up a fishing rate time series pattern where fishing is first stopped for a decade or so then ramped up over the remaining years to a very high value relative to your baseline rate from Ecopath. 
     24 1. Go to the [wiki:RunEcosim Run Ecosim] form (Time dynamic (Ecosim) > Output > Run Ecosim), select ''Groups'' from the drop-down ''Target'' menu on and then the adult pool. Using the fishing rate sketch pad, set up a fishing rate time series pattern where fishing is first stopped for a decade or so then ramped up over the remaining years to a very high value relative to your baseline rate from Ecopath. 
    2525 
    2626 2. Open the ''''S/R plot'''' form, and select the same adult group (Time dynamic (Ecosim) > Output > S/R plot).