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Simulate expected yield using the Beverton-Holt Yield-per-Recruit model for single input parameters

Source: R/yprBH_func.R
yprBH_func.Rd

Estimate yield using the Beverton-Holt Yield-per-Recruit (YPR) model. This main function accepts only single values for conditional fishing mortalitiy (cf), conditional natural mortality (cm), and a minimum length limit for harvest (minLL).

Usage

yprBH_func(minLL, cf, cm, loi = NULL, lhparms, matchRicker = FALSE)

Arguments

minLL

A single numeric representing the minimum length limit for harvest in mm.

cf

A single numeric representing conditional fishing mortality.

cm

A single numeric representing conditional natural mortality.

loi

A numeric vector for lengths of interest. Used to determine number of fish that reach desired lengths.

lhparms

A named vector or list that contains values for each N0, tmax, Linf, K, t0, LWalpha, and LWbeta. See makeLH for definitions of these life history parameters. Also see details.

matchRicker

A logical that indicates whether the yield function should match that in Ricker (). Defaults to TRUE. The only reason to changed to FALSE is to try to match output from FAMS. See the "YPR_FAMSvRICKER" article.

Value

A data.frame with the following calculated values:

  • yield is the estimated yield (in g).

  • nharvest is the number of harvested fish.

  • ndie is the number of fish that die of natural deaths.

  • nt is the number of fish at time tr (time they become harvestable size).

  • tr is the time for a fish to recruit to a minimum length limit (i.e., time to enter fishery).

  • avgwt is the average weight of fish harvested.

  • avglen is the average length of fish harvested.

  • nAtxxx is the number that reach the length of interest supplied. There will be one column for each length of interest.

  • exploitation is the exploitation rate.

  • F is the instantaneous rate of fishing mortality.

  • M is the instantaneous rate of natural mortality.

  • Z is the instantaneous rate of total mortality.

  • S is the (total) annual rate of survival.

For convenience the data.frame also contains the model input values (minLL, cf, cm, N0, Linf, K, t0, LWalpha, LWbeta, and tmax).

The data.frame also contains a notes value which may contain abbreviations for "issues" that occurred when computing the results and were adjusted for. The possible abbreviates are as follows:

  • minLL>=Linf: The minimum length limit (minLL) being explored was greater than the given asymptotic mean length (Linf). For the purpose (only) of computing the time at recruitment to the fishery (tr) the Linf was set to minLL+0.1.

  • tr<t0: The age at recruitment to the fishery (tr) was less than the hypothetical time when the mean length is zero (t0). The fish can't recruit to the fishery prior to having length 0 so tr was set to t0. This also assures that the time it takes to recruit to the fishery is greater than 0.

  • Nt<0: The number of fish recruiting to the fishery was less than 0. There cannot be negative fish, so Nt was then set to 0.

  • Nt>N0: The number of fish recruiting to the fishery was more than the number of fish recruited to the populations. Fish cannot be added to the cohort, so Nt was set to N0.

  • Y=Infinite: The calculated yield (Y) was inifinity, which is impossible and suggests some other propblem. Yield was set to NA.

  • Y<0: The calculated yield (Y) was negative, which is impossible. Yield was set to 0.

  • Nharv<0: The calculated number of fish harvested (Nharv) was negative, which is not possible. Number harvested was set to 0.

  • Nharv>Nt: The calculated number of fish harvested (Nharv) was greater than the number of fish recruiting to the fishery, which is impossible. The number harvested was set to the number recruiting to the fishery.

  • Ndie<0: The calculated number of fish recruiting to the fishery that died naturally (Ndie) was negative, which is not possible. Number that died was set to 0.

  • Ndie>Nt: The calculated number of fish recruiting to the fishery that died naturally (Ndie) was greater than the number of fish recruiting to the fishery, which is impossible. The number that died was set to the number recruiting to the fishery.

  • agvglen<minLL: The average length of harvested fish was less than the given minimum length limit being explored, which is not possible (with only legal harvest). The average length was set to the minimum length limit.

Details

Details will be filled out later

References

Ricker, W.E. 1975. Computation and interpretation of biological statistics of fish populations. Technical Report Bulletin 191, Bulletin of the Fisheries Research Board of Canada. Was (is?) from https://waves-vagues.dfo-mpo.gc.ca/library-bibliotheque/1485.pdf.

Slipke, J.W., and M.J. Maceina. 2014. Fishery analysis and modeling simulator. v1.64. American Fisheries Society, Bethesda, MD.

See also

yprBH_minLL_fixed and yprBH_minLL_var for simulating yield with multiple values of cf, cm, and minLL.

Author

Jason C. Doll, jason.doll@fmarion.edu

Examples

#' # Life history parameters to be used below
LH <- makeLH(N0=100,tmax=15,Linf=592,K=0.20,t0=-0.3,LWalpha=-5.528,LWbeta=3.273)

# Estimate yield with fixed parameters
Res_1 <- yprBH_func(minLL=355,cf=0.45,cm=0.25,
                    loi=c(200,250,300,325,350),lhparms=LH)
Res_1
#>     yield nharvest     ndie       nt       tr    avgwt   avglen  nAt200
#> 1 19606.5  19.7239 9.491238 29.21514 4.277232 994.0479 402.5024 60.2497
#>     nAt250   nAt300   nAt325   nAt350 exploitation        F         M         Z
#> 1 49.51249 39.44369 34.67882 30.10579    0.3966366 0.597837 0.2876821 0.8855191
#>        S   cf   cm minLL  N0 Linf   K   t0 LWalpha LWbeta tmax notes
#> 1 0.4125 0.45 0.25   355 100  592 0.2 -0.3  -5.528  3.273   15