MQMF (version 0.1.5)

bce: bce Baranov catch equation

Description

bce the Baranov Catch Equation. The total mortality of fish in an exploited population is made up of fish being killed by fishing and others dying naturally. We use the bce to estimate the catch (those killed by fishing). The bce has value because some fish that would be expected to die naturally can be expected to be caught and killed by fishing, so estimating the catch is rather more complex than numbers of fish available times the harvest rate, Nt x Ht. If is possible to use the Baranov Catch Equation when calculating the expected catches then it is usually better to do so.

Usage

bce(M, Fat, Nt, ages)

Value

a matrix of surviving numbers-at age, total mortality-at-age, and catch-at-age

Arguments

M

instantaneous rate of natural mortality, assumed constant

Fat

a vector of age-specific instantaneous rates of fishing mortality over the time period t, this is usually estimated by multiplying the fully selected F by the selectivity/availability at age.

Nt

The population numbers-at-age at the start of time t

ages

the ages 0:maxage used in the calculations

Examples

age <- 0:25
Ft <- -log(1 - 0.2) # harvest rate of 0.2
Faa <- rep(Ft,length(age))
M <- 0.12
Nt <- 1000
bce(M,Fat=Faa,Nt,ages=age)   # should give 188.8862