Buffer Harvest Control Rule Management Procedure

A model-free management procedure that replicates the CPUE + buffer HCR MP of the earlier albacore MSE work (cpue.ind and buffer.hcr of the FLR mse/msemodules packages; Mosqueira and Hillary 2025, IOTC-2025-WPM16-11, IOTC-2026-WPM17(MSE)-03). Unlike MSEtool::IndexTarget() with a buffer HCR (BufferHCR()), the HCR output is a multiplier on the previous TAC, so the TAC keeps changing in each management cycle while the index is outside the buffer.

Usage

BufferMP(
  Data,
  Indices = "LL1",
  IndexSource = "Survey",
  IndexRef,
  IndexWeight = NULL,
  nYears = 4,
  Metric = c("wmean", "mean"),
  Limit = 0.4,
  LowerBuffer = 0.56,
  UpperBuffer = 0.96,
  SlopeRatio = 0.1,
  DeltaDown = c(0, 0.15),
  DeltaUp = c(0, 0.15),
  TACType = c("Removals", "Landings"),
  tunepar = 1
)

Arguments

Data

A data object.

Indices

Character vector. Names of the indices in IndexSource. Default 'LL1'.

IndexSource

Character. 'Survey' (default) or 'CPUE'.

IndexRef

Numeric vector, one per index. The index level that corresponds to a status of 1 (e.g. the index at SBMSY).

IndexWeight

NULL (default, equal weights) or a numeric vector of weights, one per index.

nYears

Positive integer. Number of data years in the metric. Default 4.

Metric

Character. 'wmean' (default) or 'mean'.

Limit, LowerBuffer, UpperBuffer

Numeric. The limit and the lower and upper buffers, in units of status (index / IndexRef). Defaults 0.4, 0.56, and 0.96: the values of the earlier work (0.25, 0.35, and 0.60 in units of the index) scaled so that the limit is at 0.4 SBMSY.

SlopeRatio

Numeric. Slope of the increase above the upper buffer relative to the slope of the decrease between the limit and the lower buffer. Default 0.10.

DeltaDown, DeltaUp

Numeric vectors, length 2. Minimum and maximum proportional decrease and increase in the TAC (see MSEtool::ConstrainTAC()). Default c(0, 0.15).

TACType

Character. 'Removals' (default) or 'Landings'.

tunepar

Positive number. Tuning parameter; see Tuning.

Value

An advice object.

Details

Procedure

1. The data are aggregated to calendar years with MSEtool::AnnualData() (each index averaged over the seasons with data).

2. The index metric is the mean of each index over the last nYears data years: a weighted mean (Metric = 'wmean'), with weight 0.5 for the last year and the other 0.5 shared among the earlier years in proportion to their position (e.g. 1/12, 2/12, 3/12 for nYears = 4), or an unweighted mean (Metric = 'mean').

3. Stock status is the metric relative to IndexRef (e.g. the index level at SBMSY, IndexAtSBMSY()), combined over indices with IndexWeight.

4. The TAC multiplier is, for status x, limit L, lower buffer B1 and upper buffer B2:

   • (x / L)^2 / 2 for x <= L;

   • 0.5 (1 + (x - L) / (B1 - L)) for L < x <= B1;

   • 1 for B1 < x < B2;

   • 1 + SlopeRatio (0.5 / (B1 - L)) (x - B2) for x >= B2.

5. The TAC is the previous TAC (MSEtool::LastTAC()) times the multiplier, with the change constrained by DeltaDown and DeltaUp (MSEtool::ConstrainTAC()).

Tuning

In the earlier work the MP was tuned by the position of the upper buffer. Here tunepar sets the upper buffer to LowerBuffer + (UpperBuffer - LowerBuffer) / tunepar, so that larger values of tunepar move the upper buffer towards the lower buffer and increase the catch. tunepar = 1 uses UpperBuffer.