ReferencePoints: Biological reference points from yield-per-recruit analysis.
In sandroklippel/fishassess: Functions on fishery biology, stock assessment and management.

Description Usage Arguments Details Value Note Author(s) References See Also Examples

Biological reference points for fisheries management obtained from yield-per-recruit analysis.

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Fmax(obj)
F0.1(obj)
F0.x(obj, x=1)

obj

object of the class BH.

The yield-per-recruit analysis uses information on average individual growth, natural mortality and vulnerability to fishing.

Fmax is the fishing mortality for a given size at first capture, which maximizes the average yield from each recruit entering the fishery. It could be considered as a limit reference point for the stock.

F0.1 is the fishing mortality rate at which the slope of the yield-per-recruit curve as a function of fishing mortality is 10% of its value at the origin. The fishing mortality level F0.1 was proposed as a conservative target reference point.

F0.x is a generalization of F0.1.

The value of the reference point.

Fmax searches for the maximum between 0 and 100 of fishing mortalities. F0.1 is searched between zero and Fmax. The slope is obtained by first derivative.

Sandro Klippel

Caddy, J., 1998. A short review of precautionary reference points an some proposals for their use in data-poor situations. Vol. 379 of FAO Fisheries Technical Paper. FAO, Rome.

Caddy, J., Mahon, R., 1995. Reference points for fisheries management. Vol. 374 of FAO Fisheries Technical Paper. FAO, Rome.

Gulland, J., 1968. The concept of marginal yield from exploited fish stocks. J. Cons. CIEM 32, 256-261.

Beverton.Holt, num.deriv, optimize, uniroot

BHxxx <- Beverton.Holt(F=0.5, M=1.1, Winf=286, K=0.37, 
                       t0=-0.2, Tr=0.4, Tc=1, approxim="g")
Fmax(BHxxx)
F0.1(BHxxx)
F0.x(BHxxx,x=2)

## Not run: 

## Monte Carlo approach
## This code does not run directly with example()

F <- rep(NA, 500)
for (i in 1:500){
  F[i] <- F0.1(Beverton.Holt(
  Wt=function(t){rnorm(1,mean=VBGFw(t, Winf=3000, K=0.25,
t0=-0.2),
  sd=300)}, Tr=1, Tc=5, Tmax=25, F=1, 
  M=runif(1, min=0.175, max=0.275)))
}
library(MASS)
truehist(F, xlab="F0.1", col="white")
lines(density(F), lwd=2)

## End(Not run)