Iterative Index Target MP — IT5 • DLMtool Functions

An index target MP where the TAC is modified according to current index levels (mean index over last 5 years) relative to a target level.

IT5(x, Data, reps = 100, plot = FALSE, yrsmth = 5, mc = 0.05)

IT10(x, Data, reps = 100, plot = FALSE, yrsmth = 5, mc = 0.1)

Arguments

x: A position in the data object
Data: A data object
reps: The number of stochastic samples of the MP recommendation(s)
plot: Logical. Show the plot?
yrsmth: The number of historical years over which to average the index
mc: The maximum fractional change in the TAC among years.

Value

An object of class Rec-class with the TAC slot populated with a numeric vector of length reps

Details

The TAC is calculated as: $$\textrm{TAC}_y = C_{y-1} I_\delta$$ where $C_{y-1}$ is the catch from the previous year and $I_\delta$ is the ratio of the mean index over the past yrsmth years to a reference index level. The maximum allowable change in TAC is determined by mc: e.g mc=0.05 means that the maximum change in TAC from the previous catch is 5%.

The reference index level (Data@Iref) is assumed to be a proxy for MSY. In the MSE Iref is the index at MSY subject to observation error (Obs@Irefbiascv). Consequently the performance of these methods in MSE is strongly determined by the uncertainty the in reference index.

Functions

IT5: Maximum annual changes in TAC are 5 per cent.
IT10: Maximum annual changes are 10 per cent.

Required Data

See Data-class for information on the Data object

IT5: Ind, Iref, MPrec

IT10: Ind, Iref, MPrec

Rendered Equations

See Online Documentation for correctly rendered equations

Author

T. Carruthers

Examples

IT5(1, MSEtool::SimulatedData, plot=TRUE)

#> TAC (median) 
#>       1783.1 
IT10(1, MSEtool::SimulatedData, plot=TRUE)

#> TAC (median) 
#>      1824.35