The MP adjusts catch based on the value of the index in the current year relative to the time series mean and standard error.
ICI(x, Data, reps = 100, plot = FALSE)ICI2(x, Data, reps = 100, plot = FALSE)
A position in the data object
A data object
The number of stochastic samples of the MP recommendation(s)
Logical. Show the plot?
An object of class Rec with the TAC slot populated with a numeric vector of length reps
ICI: The catch is reduced by 0.75 if the Z-score of the current year's index is less than -0.44.
The catch is increased by 1.05 if the Z-score of the current year's index is greater than 1.96. Otherwise, the catch is held constant.
ICI2: This method is less precautionary of the two ICI MPs by allowing for a
larger increase in TAC and a lower threshold of the index to decrease the TAC. The catch is reduced by 0.75
if the Z-score of the current year's index is less than -1.96. The catch is increased by 1.25
if the Z-score of the current year's index is greater than 1.96. Otherwise, the catch is held constant.
See Online Documentation for correctly rendered equations
The TAC is calculated as:
$$\textrm{TAC}_y=C_{y-1} \alpha$$
where \(C_{y-1}\) is the catch from the previous year, and \(\alpha\) is
defined as:
$$\alpha =
\left\{\begin{array}{ll}
d & \textrm{if } I < \textrm{CI}_L \\
u & \textrm{if } I > \textrm{CI}_H \\
1 & \textrm{if } \textrm{CI}_L \leq I \leq \textrm{CI}_H \\
\end{array}\right.
$$
where \(I\) is the index in the most recent year, \(d\) is 0.75 for ICI and ICI2,
\(u\) is 1.05 and 1.25 forICI and ICI2 respectively, and \(\textrm{CI}_L\)
and \(\textrm{CI}_L\) are the lower and upper bound of the confidence
interval of mean historical index. The confidence interval is
calculated using Z-scores described in the Functions section below.
Ernesto Jardim, Manuela Azevedo, Nuno M. Brites, Harvest control rules for data limited stocks using length-based reference points and survey biomass indices, Fisheries Research, Volume 171, November 2015, Pages 12-19, ISSN 0165-7836, https://doi.org/10.1016/j.fishres.2014.11.013
Other Index methods: GB_slope,
GB_target, Gcontrol,
Iratio, Islope1,
Itarget1_MPA, Itarget1,
ItargetE1
# NOT RUN {
ICI(1, Data=DLMtool::Atlantic_mackerel, plot=TRUE)
ICI2(1, Data=DLMtool::Atlantic_mackerel, plot=TRUE)
# }
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