sbpr: Spawning Stock Biomass-Per-Recruit Analysis

In fishmethods: Fishery Science Methods and Models

Spawning Stock Biomass-Per-Recruit Analysis

Description

Spawning stock biomass-per-recruit analysis (SSBPR) is conducted following Gabriel et al. (1989).

Usage

 sbpr(age=NULL,ssbwgt=NULL,partial=NULL,pmat=NULL,M=NULL,pF=NULL,pM=NULL,
               plus=FALSE,oldest=NULL,maxF=2,incrF=0.0001,options=c(1,2,3,4),MSP=NULL,
               SSBPR=NULL,Fsol=NULL,graph=TRUE)

Arguments

age	a numeric 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.
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 SSBPR will be calculated. SSBPR is calculated for F = 0 to maxF.
incrF	F increment for SSBPR calculation.
options	1 = generate spawning stock biomass-per-recruit values for F ranging from 0 to maxF by incrF. 2 = find a single SSBPR value for a given value of F (Fsol), 3 = find F at a specified percent maximum SSBPR (MSP), 4 = find F for a given value of SSBPR. Default = c(1,2,3,4).
Fsol	F for which to obtain a corresponding spawning biomass-per-recruits value. Default = NULL.
MSP	the percentage of maximum spawning potential (percent MSP reference point) for which F and SBPR should be determined. Default = NULL.
SSBPR	A spawning biomass-per-recruit value for which to obtain a corresponding F. Default = NULL.
graph	a logical indicating whether SSBPR versus F should be plotted for options = 1. Default=TRUE.

Details

Spawning stock biomass-per-recruit analysis is conducted following Gabriel et al. (1989). 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. Multiple options are available to abbreviate calculations.

Value

SSBPR_vs_F	For option = 1, spawning stock biomass-per-recruit values for each F increment.
SSBPR_at_Fsol	If option = 2, the SSBPR value corresponding to Fsol.
F_at_MSP	If option = 3, the F reference point corresponding to MSP.
F_at_SSBPR	If option = 4, the F corresponding to a given SSBPR.

Author(s)

Gary A. Nelson, Massachusetts Division of Marine Fisheries [e-mail]

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

ypr

Examples

data(haddock)
#Generate SSBPR versus F, and F for MSP reference point
sbpr(age=haddock$age,ssbwgt=haddock$ssbwgt,partial=haddock$partial,
pmat=haddock$pmat,M=0.2,pF=0.2, pM=0.1667,plus=FALSE,maxF=2,
incrF=0.001,MSP=30,options = c(1,3))		

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