calcPrjMMB: Calculate projected MMMB at mating based on a fishing...

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

Calculate projected MMMB at mating based on a fishing mortality rate.

Description

Function to calculate projected MMMB at mating based on a fishing mortality rate.

Usage

calcPrjMMB(
  mmbSrvCurr,
  Fm,
  theta,
  M = 0.18,
  t.sf = 3/12,
  t.fm = 4/12,
  rec = 0,
  verbose = FALSE
)

Arguments

mmbSrvCurr	current MMB at time of survey
Fm	assumed fishing mortality rate
theta	\theta, the average ratio of mature male discard mortality to MMB at fishing
M	assumed rate of natural mortality
t.sf	time from survey to fishery
t.fm	time from fishery to mating
rec	assumed recruitment to MMB at mating (0 for PIBKC assessment)
verbose	flag (T/F) to print intermediate output

Details

MMB-at-mating is projected from survey MMB for a given directed fishing mortality using:

1. MMB_f = MMB_s \cdot exp(-M \cdot t_{sf})

2. M_r = MMB_f \cdot (1-exp(-F))

3. M_d = \theta \cdot MMB_f

4. MMB_m = [MMB_f - (M_r + M_d)] \cdot exp(-M \cdot t_{fm}) + R

where MMB_s is MMB at the time of the survey, M is the rate of natural mortality, t_{sf} is the time (as a fraction of the year) between the survey and fishery, MMB_f is MMB just before the fishery, F is the retained mortality rate in the directed fishery, M_r is retained catch mortality, \theta is the fraction of MMB_f killed as discards, M_d is discard catch mortality, t_{fm} is the time (as fraction of the year) between the fishery and mating, and R is the assumed recruitment to the mature male component of the stock at mating.

Value

list with elements:

• mmb = MMB_m (t), MMB at time of mating (includes recruitment)

• retM = retained mortality (t)

• dscM = discard mortality on MMB (t) (NOT total discard mortality)

• mmbBF = projected MMB just before the fishery (t)

• mmbAF = projected MMB just after the fishery (t)

• mmbBM = projected MMB just before mating (t)

• rec = assumed recruitment to MMB at mating (t)

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