`ICI.Rd`

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)
```

- 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?

An object of class `Rec-class`

with the `TAC`

slot populated with a numeric vector of length `reps`

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 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.

`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

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

```
ICI(1, Data=MSEtool::Atlantic_mackerel, plot=TRUE)
#> TAC (median)
#> 14.14525
ICI2(1, Data=MSEtool::Atlantic_mackerel, plot=TRUE)
#> TAC (median)
#> 13.89096
```