calcOFL: Calculate the OFL using a Tier 4 approach.

In wStockhausen/rPIBKC: Package to run the PIBKC stock assessment

Calculate the OFL using a Tier 4 approach.

Description

Function to calculate the OFL using a Tier 4 approach.

Usage

calcOFL(
  mmbSrvCurr,
  Bmsy,
  theta,
  M = 0.18,
  gamma = 1,
  alpha = 0.1,
  beta = 0.25,
  t.sf = 3/12,
  t.fm = 4/12,
  pct.male = 0.5,
  rec = 0,
  verbose = FALSE
)

Arguments

mmbSrvCurr	"current" MMB at time of survey
Bmsy	B_{MSY} (see calcBmsy)
theta	value for \theta (see calcTheta)
M	natural mortality rate
gamma	value for the Tier 4 \gamma constant (in Tier 4: F_{OFL_{max}} = \gamma \cdot M)
alpha	value for the Tier 4 \alpha constant (the x-intercept of the sloping control rule)
beta	value for the Tier 4 \beta constant (the threshold for MMB/B_{MSY} to allow directed fishing)
t.sf	time (fraction of year) from survey to (pulse) fishery
t.fm	time (as fraction of year) from (pulse) fishery to mating
pct.male	assumed male percentage
rec	assumed recruitment to mature male biomass at time of mating (added to MMB after fishery)
verbose	flag (T/F) to print intermediate output

Details

In Tier 4, the F_{OFL} is derived from a "kinked" harvest control rule based on the ratio of MMB-at-mating for the assessment year to B_{MSY}. However, when the assessment year is the current year (so that the OFL is calculated for the upcoming fishing season), the MMB-at-mating itself depends what will be caught by the fishery, which in turns depends on the OFL and (possibly) the F_{OFL}. Consequently, the calculation for OFL uses the following iterative procedure:

1. "guess" a value for F_{OFL} (F_{OFL_{max}} = \gamma \cdot M is used)

2. determine the OFL corresponding to fishing at F_{OFL}

3. project MMB-at-mating from the "current" survey MMB (raw or averaged) and the OFL

4. use the harvest control rule to determine the F_{OFL} corresponding to the projected MMB-at-mating

5. update the "guess" in 1. for the result in 4.

6. repeat steps 2-5 until the process has converged, yielding self-consistent values for F_{OFL} and MMB-at-mating

Value

List with elements:

• prjMMB - projected MMB to time of mating (in t)

• Bmsy - Tier 4 B_{MSY} (in t),

• status - Tier 4 status ("overfished" or "not overfished")

• maxFofl - max allowed F_{OFL} = \gamma \cdot M for Tier 4

• Fofl - Tier 4 F_{OFL}, based on the Tier 4 harvest control rule

• retOFL - retained portion of total OFL (in t)

• dscOFL - discard portion of total (male + female) OFL (in t)

• OFL - total OFL (in t)

• dscOFL - discard portion of mature male OFL (in t)

• mmbBF - MMB just before fishery

• mmbAF - MMB just after fishery

• mmbBM - MMB just before mating

• rec - recruitment added to mmbBM to obtain prjMMB

• status ratio - numerical ratio describing status

wStockhausen/rPIBKC documentation built on April 25, 2023, 6:50 p.m.