Changes between Version 5 and Version 6 of EwEugProduction


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Timestamp:
2010-11-18 02:52:49 (9 years ago)
Author:
shermanl
Comment:

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  • EwEugProduction

    v5 v6  
    33Production refers to the elaboration of tissue (whether it survives or not) by a group over the period considered, expressed in whatever currency has been selected. Total mortality, under the condition assumed for the construction of mass-balance models, equal to production over biomass (Allen, 1971). Therefore, one can use estimates of total mortality (''Z'') as input values for the production over biomass ratio (''P/B'') in Ecopath models. Some examples of how to obtain ''P/B ''values is given below. 
    44 
    5 Even if the parameter is labelled ‘production/biomass’ in EwE, what should be entered is actually the mortality rate. An example, if you have a juvenile group and use a bioenergetic model to calculate the production, you should subtract the amount that is recruited to the adult group from the production in order to the actual mortality, which is what Ecosim needs to work with. Production over biomass is entered on the [[Basic input.htm|Basic input]] form. See [[Mortality coefficients.htm|Mortality coefficients]] and [[Predation mortality.htm|Predation mortality]] for description of Ecopath’s estimates of different mortality components in the system. 
     5Even if the parameter is labelled 'production/biomass' in EwE, what should be entered is actually the mortality rate. An example, if you have a juvenile group and use a bioenergetic model to calculate the production, you should subtract the amount that is recruited to the adult group from the production in order to the actual mortality, which is what Ecosim needs to work with. Production over biomass is entered on the [EwEugBasicInput Basic input] form. See [EwEugMortalityCoefficients Mortality coefficients] and [EwEugPredationMortality Predation mortality] for description of Ecopath's estimates of different mortality components in the system. 
    66 
    77'''Total mortality catch curves''' 
     
    1717where, ''M'' is the natural mortality (/year), ''K'' is the curvature parameter of the VBGF (/year), ''L'',,''∞'',, is the asymptotic length (total length, cm), and ''Tc'' is the mean habitat (water) temperature, in °C . 
    1818 
    19 In equilibrium situations, fishing mortality can be estimated directly from the catch (or more precisely from the ‘yield’, which expresses catches (including discards) in weight): 
     19In equilibrium situations, fishing mortality can be estimated directly from the catch (or more precisely from the 'yield', which expresses catches (including discards) in weight): 
    2020 
    2121Fishing mortality = yield / biomass 
     
    2929'''[[Image(wiki:EwEugImages:08000017.png)]] Eq. 17''' 
    3030 
    31 where ''L,,∞,,'' is the asymptotic length, i.e., the mean size the individuals in the population would reach if they were to live and grow indefinitely, K is the VBGF curvature parameter (expressing the rate at which ''L,,∞,,'' is approached), [[Image(wiki:EwEugImages:08000018.png)]] is the mean length in the population, computed from L’ upward. Here, L’ represents the mean length at entry into the fishery, assuming knife-edge selection. Note that [[Image(wiki:EwEugImages:08000018.png)]] must be > L’. 
     31where ''L,,∞,,'' is the asymptotic length, i.e., the mean size the individuals in the population would reach if they were to live and grow indefinitely, K is the VBGF curvature parameter (expressing the rate at which ''L,,∞,,'' is approached), [[Image(wiki:EwEugImages:08000018.png)]] is the mean length in the population, computed from L' upward. Here, L' represents the mean length at entry into the fishery, assuming knife-edge selection. Note that [[Image(wiki:EwEugImages:08000018.png)]] must be > L'.