fishmethods (version 1.3-0)

ypr: Yield-Per-Recruit Analysis

Description

Yield-per-recruit (YPR) analysis is conducted following the modified Thompson-Bell algorithm. Reference points Fmax and F0.1 are calculated.

Usage

ypr(age = NULL, wgt = NULL, partial = NULL, M = NULL,
 plus = FALSE, oldest = NULL, maxF = 2, incrF = 0.001)

Arguments

age

the vector of cohort ages, e.g. c(1,2,3,4,5). If the last age is a plus group, do not add a "+" to the age.

wgt

the vector of catch weights for each age, e.g. c(0.2,0.4,0.7,1.0,1.2). Length of vector must correspond to the length of the age vector.

partial

the partial recruitment vector applied to fishing mortality (F) to obtain partial F-at-age. Length of the partial recruitment vector must correspond to the length of the age vector.

M

vector containing a single natural mortality (M) rate if M is assumed constant over all ages, or a vector of Ms, one for each age. If the latter, the vector length must correspond to the length of the age vector.

plus

a logical value indicating whether the last age is a plus-group. Default is FALSE.

oldest

if plus=TRUE, a numeric value indicating the oldest age in the plus group.

maxF

the maximum value of F range over which YPR will be calculated. YPR is calculated for F = 0 to maxF.

incrF

F increment for YPR calculation.

Value

• Reference_Points
  F and yield-per-recruit values for Fmax and F0.1
• F_vs_YPR
  Yield-per-recruit values for each F increment

Details

Yield-per-recruit analysis is conducted following the modified Thompson-Bell algorithm. Reference points Fmax and F0.1 are calculated. If the last age is a plus-group, the cohort is expanded to the oldest age and the wgt, partial, and M values for the plus age are applied to the expanded cohort ages.

References

Gabriel, W. L., M. P. Sissenwine, and W. J. Overholtz. 1989. Analysis of spawning stock biomass per recruit: an example for Georges Bank haddock. North American Journal of Fisheries Management 9: 383-391.

See Also

sbpr

Examples

data(haddock)
ypr(age=haddock$age,wgt=haddock$ssbwgt,partial=haddock$partial,M=0.4,
plus=TRUE,oldest=100,maxF=2,incrF=0.001)