Spawning stock biomass-per-recruit(SBPR) analysis is conducted following Gabriel et al. (1989). Reference points of F and SBPR for a percentage of maximum spawning potential are calculated.

```
sbpr(age = NULL, ssbwgt = NULL, partial = NULL, pmat = pmat,
M = NULL, pF = NULL, pM = NULL, MSP = 40, plus = FALSE,
oldest = NULL, maxF = 2, incrF = 1e-04, graph = TRUE)
```

age

vector of cohort ages. If the last age is a plus group, do not add a "+" to the age.

ssbwgt

vector of spawning stock weights for each age. Length of vector must correspond to the length of the age vector.

partial

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

pmat

proportion of mature fish at each age. Length of this vector must match 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 match the length of the age vector.

pF

the proportion of fishing mortality that occurs before spawning.

pM

the proportion of natural mortality that occurs before spawning.

MSP

the percentage of maximum spawning potential (percent MSP reference point) for which F and SBPR should be calculated.

plus

a logical indicating whether the last age is a plus-group. Default=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 SBPR will be calculated. SBPR is calculated for F = 0 to maxF.

incrF

F increment for SBPR calculation.

graph

a logical indicating whether SPR and Percent Max SPR versus F should be plotted. Default=TRUE.

F and SBPR values for the percentage MSP

Spawning stock biomass-per-recruit values for each F increment

Spawning stock biomass-per-recruit analysis is conducted following Gabriel et al. (1989). The F and SBPR for the
percentage maximum spawning potential reference point are calculated. If the last age is a plus-group, the cohort
is expanded to the `oldest`

age and the `ssbwgt`

, `partial`

, `pmat`

, 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.

```
# NOT RUN {
data(haddock)
sbpr(age=haddock$age,ssbwgt=haddock$ssbwgt,partial=haddock$partial,
pmat=haddock$pmat,M=0.2,pF=0.2, pM=0.1667,MSP=30,plus=FALSE,maxF=2,
incrF=0.001)
# }
```

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