Yield-per-recruit (YPR) analysis is conducted following the modified Thompson-Bell algorithm. Reference points Fmax and F0.1 are calculated.
ypr(age = NULL, wgt = NULL, partial = NULL, M = NULL,
plus = FALSE, oldest = NULL, maxF = 2, incrF = 0.001, graph = TRUE)
F and yield-per-recruit values for Fmax and F0.1
Yield-per-recruit values for each F increment
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.
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.
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.
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.
a logical value indicating whether the last age is a plus-group. Default is FALSE.
if plus=TRUE, a numeric value indicating the oldest age in the plus group.
the maximum value of F range over which YPR will be calculated. YPR is calculated for F = 0 to maxF.
F increment for YPR calculation.
logical indicating whether YPR versus F should be plotted. Default=TRUE.
Gary A. Nelson, Massachusetts Division of Marine Fisheries gary.nelson@mass.gov
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.
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.
sbpr
data(haddock)
ypr(age=haddock$age,wgt=haddock$ssbwgt,partial=haddock$partial,M=0.4,
plus=TRUE,oldest=100,maxF=2,incrF=0.01)
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