`GB_target.Rd`

An MP similar to SBT2 that modifies a time-series of catch recommendations and aims for target catch rate and catch level based on BMSY/B0 and MSY, respectively.

GB_target(x, Data, reps = 100, plot = FALSE, w = 0.5)

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? |

w | A gain parameter |

An object of class `Rec-class`

with the `TAC`

slot populated with a numeric vector of length `reps`

The TAC is calculated as: If \(I_\textrm{recent} \geq I_0\): $$\textrm{TAC}= C_\textrm{ref} \left(w + (1-w)\frac{I_\textrm{rec}-I_0}{I_\textrm{target}-I_0} \right) $$

else: $$\textrm{TAC}= wC_\textrm{ref} \frac{I_\textrm{rec}}{I_0}^2$$

where \(C_\textrm{ref}\) is a reference catch assumed to be a proxy for MSY (`Data@Cref`

),
*w* is a gain parameter,
\(I_\textrm{rec}\) is the average index over the last 4 years,
\(I_\textrm{target}\) is the target Index (`Data@Iref`

), and
\(I_0\) is 0.2 x the average index over the past 5 years.

In the MSE \(C_\textrm{ref}\) is the calculated MSY subject to observation error
defined in `Obs@CV_Cref`

, and \(I_\textrm{target}\) is assumed to be the index at MSY subject
to observation error (`Obs@CV_Iref`

). Consequently, the performance of this method in the MSE
is strongly determined by the specified uncertainty for these parameters.

The TAC is subject to the following conditions:

if next TAC > 1.2 last catch, then TAC = 1.2 last catch

if next TAC < 0.8 last catch, then TAC = 0.8 last catch

See `Data-class`

for information on the `Data`

object

`GB_target`

: Cref, Ind, Iref

See Online Documentation for correctly rendered equations

Geromont, H.F. and Butterworth, D.S. 2014. Complex assessment or simple management procedures for efficient fisheries management: a comparative study. ICES J. Mar. Sci. doi:10.1093/icesjms/fsu017

Other Index methods:
`GB_slope()`

,
`Gcontrol()`

,
`ICI()`

,
`Iratio()`

,
`Islope1()`

,
`Itarget1_MPA()`

,
`Itarget1()`

,
`ItargetE1()`

T. Carruthers

#> TAC (median) #> 1291.749