A fishery is a set of fleets that share a time horizon. Each fleet has a nominal effort trend, process noise on effort that is common to all species (so species caught by the same fleet share effort anomalies) and an optional annual efficiency increase (effort creep) that raises fishing mortality but is not visible in the nominal effort index.
Usage
fishery(
fleets,
years,
trends,
sigmaE = 0.15,
creep = 0,
creep_start = NULL,
name = "fishery",
seed = 123
)
validate_fishery(x)
fishery_years(x)Arguments
- fleets
character vector of fleet names.
- years
integer vector of years (first year = unfished start).
- trends
named list of
effort_trend()objects, one per fleet.- sigmaE
lognormal SD of the effort process noise (shared across species); scalar or one value per fleet.
- creep
annual efficiency increase per fleet (0.02 = 2% per year).
- creep_start
first year of creep per fleet (default: first year).
- name
a label.
- seed
seed for the effort realisation; every species built with this fishery sees the same effort.
- x
a
floss_fishery.
Details
Fishing mortality of species \(s\) by fleet \(f\) in year \(y\) is
$$F_{s,f,y} = q_{s,f}\,\eta_{f,y}\,E_{f,y},\quad
\eta_{f,y} = (1 + c_f)^{\max(0,\,y - y^{c}_f)},$$
where \(E\) is nominal effort (trend x lognormal noise), \(c_f\) the
creep rate and \(q_{s,f}\) the species catchability, set in
species() as relative catchability x \(F_{MSY}\).
Examples
fishery(fleets = c("traps", "linefish"), years = 1980:2025,
trends = list(traps = effort_trend(fhi = 1, flo = 0.8),
linefish = effort_trend(fhi = 2, flo = 1)))
#> FLOSS fishery 'fishery': 2 fleets, 1980-2025
#> fleet trend sigmaE creep creep_start
#> traps fudc(e0=0.05, hi=1, lo=0.8, breaks=0.5/0.75) 0.15 0 1980
#> linefish fudc(e0=0.05, hi=2, lo=1, breaks=0.5/0.75) 0.15 0 1980