DLMtool (version 5.2)

SPmod: Surplus production based catch-limit modifier

Description

An MP that makes incremental adjustments to TAC recommendations based on the apparent trend in surplus production. Based on the theory of Mark Maunder (IATTC)

Usage

SPmod(x, Data, reps = 100, plot = FALSE, alp = c(0.8, 1.2), bet = c(0.8,
  1.2))

Arguments

x

A position in a data-limited methods data object

Data

A data-limited methods data object

reps

The number of stochastic samples of the MP recommendation(s)

plot

Logical. Show the plot?

alp

Condition for modifying the TAC (bounds on change in abundance)

bet

Limits for how much the TAC can change among years

Value

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

A numeric vector of TAC recommendations

Required Data

See '>Data for information on the Data object

SPmod: Cat, Ind

Rendered Equations

See Online Documentation for correctly rendered equations

Details

Note that this isn't exactly what Mark has previously suggested and is stochastic in this implementation.

The TAC is calculated as: $$\textrm{TAC}_y = \left\{\begin{array}{ll} C_{y-1} \textrm{bet}_1 & \textrm{if } r < \alpha_1 \\ C_{y-1} & \textrm{if } \alpha_1 < r < \alpha_2 \\ \textrm{bet}_2 (b_2 - b_1 + C_{y-2} ) & \textrm{if } r > \alpha_2 \\ \end{array}\right. $$ where \(\textrm{bet}_1\) and \(\textrm{bet}_2\) are elements in bet, \(r\) is the ratio of the index in the most recent two years, \(C_{y-1}\) is catch in the previous year, \(b_1\) and \(b_2\) are ratio of index in \(y-2\) and \(y-1\) over the estimate of catchability \(\left(\frac{I}{A}\right)\), and \(\alpha_1\), \(\alpha_2\), and \(\alpha_3\) are specified in argument alp.

References

http://www.iattc.org/Meetings/Meetings2014/MAYSAC/PDFs/SAC-05-10b-Management-Strategy-Evaluation.pdf

See Also

Other Surplus production MPs: Fadapt, Rcontrol, SPMSY, SPSRA, SPslope

Examples

# NOT RUN {
SPmod(1, Data=DLMtool::Atlantic_mackerel, plot=TRUE)
# }