# ICI: Index Confidence Interval In DLMtool: Data-Limited Methods Toolkit

## Description

The MP adjusts catch based on the value of the index in the current year relative to the time series mean and standard error.

## Usage

 ```1 2 3``` ```ICI(x, Data, reps = 100, plot = FALSE) ICI2(x, Data, reps = 100, plot = FALSE) ```

## 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?

## Details

The TAC is calculated as:

\textrm{TAC}_y=C_{y-1} α

where C_{y-1} is the catch from the previous year, and α is defined as:

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 for`ICI` 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.

## Value

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

## Functions

• `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.

## Required Data

See Data for information on the `Data` object

`ICI`: Cat, Ind

`ICI2`: Cat, Ind

## Rendered Equations

See Online Documentation for correctly rendered equations

## Author(s)

Coded by Q. Huynh. Developed by Jardim et al. (2015)

## References

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`
 ```1 2 3``` ```ICI(1, Data=DLMtool::Atlantic_mackerel, plot=TRUE) ICI2(1, Data=DLMtool::Atlantic_mackerel, plot=TRUE) ```