Calculate MSY

Calculate maximum sustainable yield (MSY) reference points across multiple posterior iterations, accounting for uncertainty in recruitment and population dynamics.

Usage

get_MSY2(
  proj_inputs,
  min_increase = 0,
  search_type = 1,
  ssb_lim = 0.2,
  plim = 0.05,
  pcrash = 0.2,
  Fmult_start = 0.2
)

Arguments

proj_inputs

list of inputs prepared for projection, including SSB0 as an [n_iter, n_region] matrix, or an [n_iter, 1] matrix holding the all-region total. Per-region RelSSB is only returned in the former case.

min_increase

in terms of tons, minimum increase required to increase U

search_type

default = 1 for exploitation rate, 2 for catch

ssb_lim

default = 0 to find theoretical MSY, 0.2 to ensure above soft limit

plim

probability of falling below ssb_lim used for reference level, default = 0.05

pcrash

probability of U going too high to sustain population, default = 0.2

Fmult_start

Starting point for Fmult, default = 0.2

Value

a list with save_df (median summary of the totals at every multiplier tried), msy_df and ref_df (per-iteration totals at the MSY and reference multipliers), and msy_region_df and ref_region_df (the same iterations broken down by region).

Details

The search is driven by all-region totals: catch and adjusted vulnerable biomass are summed over regions, and relative spawning biomass is the total SSB in the final projection year over the total \(SSB_0\). One multiplier is found for the whole model. For a single-region model this is identical to using that region on its own. The per-region breakdown behind each total is returned alongside the totals. Use get_reference_region to give each region its own multiplier instead.

proj_inputs must be the MCMC form produced by prepare_proj (each posterior quantity carrying a leading iteration dimension), plus an SSB0 element supplied by the caller.