Changes between Version 1 and Version 2 of EwEugProduction
 Timestamp:
 20100128 14:39:42 (13 years ago)
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EwEugProduction
v1 v2 5 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.htmBasic input]] form. See [[Mortality coefficients.htmMortality coefficients]] and [[Predation mortality.htmPredation mortality]] for description of Ecopath’s estimates of different mortality components in the system. 6 6 7 === Total mortality catch curves === 7 '''Total mortality catch curves''' 8 8 9 9 Total mortalities can be estimated from catch curves, i.e., from catch composition data, either in terms of agestructured catch curves; (Robson and Chapman, 1961), or of lengthconverted catch curves (Pauly et al., 1995). The estimation can be carried out using appropriate software for analysis, such as the FiSAT package (Gayanilo et al., 1996). 10 10 11 === Total mortality from sum of components === 11 '''Total mortality from sum of components''' 12 12 13 13 Production rate is the sum of natural mortality (''M = M0'' + ''M2'') and fishing mortality (''F''), i.e., ''Z'' = ''M'' + ''F''. In the absence of catchatage data from an unexploited population, natural mortality for finfish can be estimated from an empirical relationship (Pauly, 1980) linking ''M'', two parameters of the von Bertalanffy Growth Function (VBGF) and mean environmental temperature, i.e., … … 23 23 where the yield is a rate, (e.g., t/km²/year), the biomass lacks a time dimension, (i.e., is expressed as t/km²), and thus the fishing mortality is an instantaneous rate, (e.g., per year). 24 24 25 === Total mortality from average length === 25 '''Total mortality from average length''' 26 26 27 27 Beverton and Holt (1957) showed that total mortality (Z = P/B), in fish population whose individuals grow according to the von Bertalanffy Growth Function (VBGF), can be expressed by: