Changes between Version 3 and Version 4 of EwEugProduction


Ignore:
Timestamp:
2010-01-28 14:52:18 (9 years ago)
Author:
varunr
Comment:

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  • EwEugProduction

    v3 v4  
    1313Production rate is the sum of natural mortality (''M = M0'' + ''M2'') and fishing mortality (''F''), i.e., ''Z'' = ''M'' + ''F''. In the absence of catch-at-age 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., 
    1414 
    15 [[Image(wiki:EwEugImages:08000016.png)]] 
    16  Eq. 16''' 
     15'''[[Image(wiki:EwEugImages:08000016.png)]] Eq. 16''' 
    1716 
    1817where, ''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 . 
     
    2827Beverton 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: 
    2928 
    30 ../Resources/Images/08000017.png 
     29'''[[Image(wiki:EwEugImages:08000017.png)]] Eq. 17''' 
    3130 
    3231where ''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), ../Resources/Images/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 ../Resources/Images/08000018.png must be > L’.