ypr is an R package that implements equilibrium-based yield per recruit methods. Yield per recruit methods can used to estimate the optimal yield for a fish population (Walters and Martell 2004). The yield can be based on the number of fish caught (or harvested) or biomass for all fish or just large (trophy) individuals.
The key life history parameters are
k) and mean maximum length (Linf) from the Von Bertalanffy growth curveLs)Lv)n)Rk)The calculations do not account for stochasticity, predator-prey dynamics, angler responses or density-dependent growth.
A shiny app is available at https://poissonconsulting.shinyapps.io/shinyypr/.
library(ypr)
population <- ypr_population(Rk = 5, Ls = 50, Rmax = 100, rho = 0.6)
ypr_plot_schedule(population, x = "Length", y = "Spawning")
head(ypr_tabulate_schedule(population))
#> # A tibble: 6 x 11
#> Age Length Weight Fecundity Spawning NaturalMortality Vulnerability
#> <int> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 1 13.9 27.0 27.0 3.13e-56 0.2 3.13e-56
#> 2 2 25.9 174. 174. 2.91e-29 0.2 2.91e-29
#> 3 3 36.2 476. 476. 1.04e-14 0.2 1.04e-14
#> 4 4 45.1 918. 918. 3.46e- 5 0.2 3.46e- 5
#> 5 5 52.8 1469. 1469. 9.95e- 1 0.2 9.95e- 1
#> 6 6 59.3 2090. 2090. 1.00e+ 0 0.2 1.00e+ 0
#> # … with 4 more variables: Retention <dbl>, FishingMortality <dbl>,
#> # Survivorship <dbl>, FishedSurvivorship <dbl>
head(ypr_tabulate_fish(population))
#> # A tibble: 6 x 7
#> Age Survivors Spawners Caught Harvested Released HandlingMortalities
#> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 1 70.1 2.19e-54 4.39e-55 1.76e-55 2.63e-55 0
#> 2 2 56.1 1.63e-27 3.26e-28 1.30e-28 1.96e-28 0
#> 3 3 44.9 4.68e-13 9.36e-14 3.74e-14 5.62e-14 0
#> 4 4 35.9 1.24e- 3 2.48e- 4 9.93e- 5 1.49e- 4 0
#> 5 5 28.7 2.86e+ 1 5.72e+ 0 2.29e+ 0 3.43e+ 0 0
#> 6 6 21.1 2.11e+ 1 4.23e+ 0 1.69e+ 0 2.54e+ 0 0
ypr_tabulate_sr(population)
#> # A tibble: 3 x 7
#> Type pi u Eggs Recruits Spawners Fecundity
#> <chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 unfished 0 0 286350. 80 159. 3600.
#> 2 actual 0.2 0.08 167831. 70.1 108. 3112.
#> 3 optimal 0.458 0.183 84129. 54.0 63.7 2641.ypr_tabulate_yield(population)
#> # A tibble: 2 x 8
#> Type pi u Yield Age Length Weight Effort
#> <chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 actual 0.2 0.08 8.63 7.67 65.8 3112. 2.12
#> 2 optimal 0.458 0.183 11.7 6.87 62.6 2641. 5.82
ypr_plot_yield(population)
library(ggplot2)
populations <- ypr_populations(Rk = c(3, 7), Ls = c(40, 60), Rmax = 100)
ypr_plot_yield(populations, plot_values = FALSE) +
facet_grid(Rk ~ Ls)
To install the latest release from CRAN
To install the developmental version from GitHub
For more information see the Get Started vignette.
To interactively explore the effects of altering individual parameters on the schedule, stock-recruitment and yield see the ypr shiny app.
Development of ypr was partially supported by the Habitat Conservation Trust Foundation and the Ministry of Forests, Lands and Natural Resource Operations.
The hex was designed by The Forest.
Please report any issues.
Pull requests are always welcome.
Please note that the ypr project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.
Walters, Carl J., and Steven J. D. Martell. 2004. Fisheries Ecology and Management. Princeton, N.J: Princeton University Press.