Eggs-Per-Recruit Analysis

Description

Eggs-per-recruit(EPR) analysis is conducted following Gabriel et al. (1989) except fecundity-at-age is substituted for weight-at-age. Reference points of F and EPR for percentage of maximum spawning potential are calculated.

Usage

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epr(age = NULL, fecund = NULL, partial = NULL, pmat = pmat,
 M = NULL, pF = NULL, pM = NULL, MSP = 40, plus = FALSE,
 oldest = NULL, maxF = 2, incrF = 1e-04)

Arguments

age

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

fecund

vector of fecundity (number of eggs per individual) 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 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 SBPR will be calculated. SBPR is calculated for F = 0 to maxF.

incrF

F increment for SBPR calculation.

Details

Eggs-per-recruit analysis is conducted following Gabriel et al. (1989). The F and EPR 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 fecund, partial, pmat, and M values for the plus age are applied to the expanded cohort ages.

Value

Reference_Points

F and EPR values for the percentage MSP

EPR_vs_F

Eggs-per-recruit values for each F increment

Author(s)

Gary A. Nelson, Massachusetts Division of Marine Fisheries gary.nelson@state.ma.us

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 sbpr

Examples

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    data(menhaden)
	epr(age=menhaden$age,fecund=menhaden$fecundity,partial=menhaden$partial,
	pmat=menhaden$pmat,M=menhaden$M,pF=0,pM=0,MSP=40,plus=TRUE,maxF=4,incrF=0.01,oldest=10)

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