Beverton-Holt stock recruit curve

Beverton and Holt (1957) stock-recruit curve with habitat constraints. Default parameter values are tuned to predict larval recruitment assuming a carrying capacity for spawning adults of 100 fish per acre. See details.

Usage

beverton_holt(
  a = 250000,
  S = 100,
  b = 0.21904,
  acres = 1,
  error = c("multiplicative", "additive"),
  age_structured = FALSE
)

Arguments

a

Ratio of recruits per spawner. Density independent parameter equivalent to the slope near S = 0. By default specified as potential annual fecundity.

S

Spawning stock abundance per acre. Numeric vector with one or more elements.

b

Density-dependent parameter. By default specified on a per-acre basis (will be divided by acres in function)

acres

Surface area (in acres) of habitat units.

error

Character string indicating whether to use 'multiplicative' or 'additive' error structure. Defaults to error = 'multiplicative'.

age_structured

Logical indicating whether to return age-structured, density-dependent recruitment from the Beverton-Holt curve. If TRUE then a vector of length = max age must be passed to S.

Value

A numeric vector with one or more elements representing age-1 recruits (downstream migrants in freshwater).

Details

The primary use of this function in the anadrofish package is to predict number of larval recruits in a river based on the number of fish within a functional habitat unit, and the number of surface acres of habitat in the same unit. However, the number of potential uses is flexible. Passing a single value to each argument would result in calculation of a single recruitment value. Alternatively, passing a vector to one of the default arguments allows the user to explore values of recruitment over a range of each input.

Under the current implementation, it is recommended that the user pass multiple values to only a single argument per call. Otherwise, we recommend conducting more in-depth sensitivity explorations by use of single values applied under a boot-strapping, or Monte Carlo approach.

References

Beverton, R. J. H. and S. J. Holt. 1957. On the Dynamics of Exploited Fish Populations, Fisheries Investigations (Series 2), Volume 19. United Kingdom Ministry of Agriculture and Fisheries, 533 pp.

Examples

# Example usage
if (FALSE) { # \dontrun{
  
# Run Beverton-Holt model to predict number
# of age-0 recruits in freshwater under 
# varying habitat amount with 100 fish and
# default parameter settings.
  
# Start by making a sequence of habitat amounts (acres)
  acres = seq(0, 100, 1)
  
# Run the Beverton-Holt curve for 100 individuals
# in varying habitats with default a and b parameters
  recruits = beverton_holt(S=100, acres = seq(0,1000,10))
  
# Plot the results
  plot(x = acres, y = recruits, type='l')
  
} # }