Changes between Version 5 and Version 6 of EwEugForagingTimeAndPredationRisk


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Timestamp:
2010-01-28 16:18:57 (10 years ago)
Author:
varunr
Comment:

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  • EwEugForagingTimeAndPredationRisk

    v5 v6  
    99In Ecosim a simple functional form for ''T''''it'' is implemented that will result in near constant feeding rates, but changing time at risk to predation, in situations where rate of effective search ''a'',,''ji'',, is the main factor limiting food consumption rather than prey behaviour as measured by ''v'',,''ji'',,. This is implemented in form of the relationship: 
    1010 
    11 ../Resources/Images/0800002A.png''' Eq. 65''' 
     11[[Image(wiki:EwEugImages:0800002A.png)]] ''' Eq. 65''' 
    1212 
    1313where, a is a user-defined Feeding time adjustment rate [0, 1] on the Ecosim [[Group info.htm#_Read_time_series|Group info]] form; ''c,,i,opt,,'' is the (internally computed) feeding rate that optimizes feeding rate versus mortality risk for ''i''; ''c,,i,t-1,,'' is the consumption/biomass ratio in the previous time step for the group. The time spent feeding is constrained by a user-defined value (Maximum relative feeding time on the ''Group info'' form with default of two times the feeding rate in the Ecopath base model). 
     
    1515The relationship between foraging time, consumption and predator biomass is illustrated in Figure 3.4. 
    1616 
    17 ../Resources/Images/0600002B.png 
     17[[Image(wiki:EwEugImages:0600002B.png)]] 
    1818 
    1919'''Figure 3.4''' Relationship between relative foraging time (''T''), ''Q/B'' and predator biomass. If ''Q/B'' is held constant the foraging time (and hence predation risk) is a linear function of the predator biomass (solid line). If ''T'' is held constant the ''Q/B'' will decrease asymptotically with predator biomass (stippled line).