Calculates the abundance of survivors after applying either a Beverton-Holt or Ricker stock-recruit relationship.
Usage
calc_SRR(N1, N2 = N1, p, capacity, type = c("BH", "Ricker"))Arguments
- N1
Numeric, the initial abundance that scales the density-independent survival term
- N2
Numeric, the initial abundance that scales the density-dependent survival term
- p
Numeric, the productivity parameter that sets the maximum survival as the initial abundance approaches zero
- capacity
Numeric, the capacity parameter that set the maximum survivors
- type
Character, the functional form of the stock-recruit relationship
Value
calc_SRRcalculates the abundance of survivorscalc_SRRparscalculates the alpha and beta terms when the productivity parameter is in terms of abundance but N1 and N2 is in terms of
Details
The Beverton-Holt stock recruit relationship is of the following form: $$\textrm{Smolt} = \dfrac{\alpha N_1}{1 + \beta N_2}$$ where \(\alpha = P\), \(\beta = P/C\).
The Ricker stock recruit relationship is of the following form: $$\textrm{Smolt} = \alpha N_1 \exp(-\beta N_2)$$ where \(\alpha = P\), \(\beta = P/(Ce)\), \(e\) is Euler's number.
Productivity \(P\) is in terms of abundance per unit of \(N_1\) and \(N_2\).