Length-converted catch curve and selectivity — catch_curve

Pauly's length-converted catch curve on the pooled length samples of one source, using growth parameters (e.g. from fit_growth()): relative age \(t(L) = t_0 - \log(1 - L/L_\infty)/k\), time to grow through a bin \(\Delta t\), and \(\log(n/\Delta t)\) against \(t\). Z is minus the slope of the descending limb. Selectivity on the ascending limb is the ratio of observed to expected numbers (the descending line extrapolated back), fitted with a logistic curve.

Usage

catch_curve_length(
  data,
  species,
  source,
  linf,
  k,
  t0 = 0,
  iter = 1,
  years = NULL,
  lmax_prop = 0.95
)

Arguments

data: a floss_data or a read_dataset() list.
species: species name.
source: one fleet (or "survey").
linf, k, t0: growth parameters (cm, per year).
iter: iteration(s) (pooled).
years: years to use; default all.
lmax_prop: bins above lmax_prop x Linf are excluded.

Value

a floss_fit with pars (Z, L50, L95).