ssb_next: Calculate next yera's SSB from survivors and Fbar

In flr/FLCore: Core Package of FLR, Fisheries Modelling in R

Calculate next yera's SSB from survivors and Fbar

Description

The spawning stock biomass (SSB) of the stock gets calculated from the survivors of the previous year. This provides a value for the first year after the end of the object. Weights-at-age, maturity in this extra year are calculated as averages over the last wts.nyears.

Usage

ssb_next(x, fbar = 0, wts.nyears = 3, fbar.nyears = 3)

Arguments

x	An FLStock object containing estimates of abundance and harvesting.
fbar	The Fbar rate assumed on the extra year. Defaults to 0.
wts.nyears	Number of years in calculation of mean weight-at-age and maturity for the extra year.
fbar.nyears	Number of years in calculation of mean selectivity, natural mortality and fraction of F abnd M before spawning for the extra year.

Details

For stocks spawning later in the year, a value for the average fishing mortality, fbar, expected in that year can be provided. Mortality until spawning is then calculated, with M and selectivity assumed in the extra year to be an average of the last fbar.nyears.

Value

An FLQuant.

Examples

data(ple4)
ssb_next(ple4)
# Compare with ssb()
ssb(ple4)[, ac(2014:2017)] / ssb_next(ple4)[, ac(2014:2017)]

flr/FLCore documentation built on May 4, 2024, midnight