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

 ICI R Documentation

## Index Confidence Interval

### 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

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:

α = ≤ft\{\begin{array}{ll} d & \textrm{if } I < \textrm{CI}_L \\ u & \textrm{if } I > \textrm{CI}_H \\ 1 & \textrm{if } \textrm{CI}_L ≤q I ≤q \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.

### Value

An object of class Rec-class 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-class 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()
ICI(1, Data=MSEtool::Atlantic_mackerel, plot=TRUE)