Calculates the rate \(E_i(w)\) at which a predator of species \(i\) and weight \(w\) encounters food (grams/year).
getEncounter( params, n = params@initial_n, n_pp = params@initial_n_pp, n_other = params@initial_n_other )
| params | A MizerParams object |
|---|---|
| n | A matrix of species abundances (species x size). |
| n_pp | A vector of the plankton abundance by size |
| n_other | A list of abundances for other dynamical components of the ecosystem |
A two dimensional array (predator species x predator size)
The encounter rate has contributions from the encounter of fish prey and of
plankton. This is determined by summing over all prey species and the
plankton spectrum and then integrating over all prey sizes \(w_p\),
weighted by predation kernel
\(\phi(w,w_p)\):
$$
E_{e.i}(w) = \gamma_i(w) \int
\left( \theta_{ip} N_R(w_p) + \sum_{j} \theta_{ij} N_j(w_p) \right)
\phi_i(w,w_p) w_p \, dw_p.
$$
Here \(N_j(w)\) is the abundance density of species \(j\) and
\(N_R(w)\) is the abundance density of plankton.
The overall prefactor \(\gamma_i(w)\) determines the predation power of the
predator. It could be interpreted as a search volume and is set with the
setSearchVolume function. The predation kernel
\(\phi(w,w_p)\) is set with the setPredKernel function. The
species interaction matrix \(\theta_{ij}\) and the plankton interaction
vector \(\theta_{ip}\) are set with setInteraction.
The encounter rate is multiplied by \(1-f_0\) to obtain the consumption rate,
where \(f_0\) is the feeding level calculated with getFeedingLevel.
This is used by the project function for performing simulations.
The function returns values also for sizes outside the size-range of the species. These values should not be used, as they are meaningless.
Other rate functions:
getEGrowth(),
getEReproAndGrowth(),
getERepro(),
getFMortGear(),
getFMort(),
getFeedingLevel(),
getMort(),
getPlanktonMort(),
getPredMort(),
getPredRate(),
getRDD(),
getRDI(),
getRates(),
getStarvMort()
if (FALSE) { data(NS_species_params_gears) data(inter) params <- newMultispeciesParams(NS_species_params_gears, inter) # Run simulation with constant fishing effort for all gears for 20 years sim <- project(params, t_max = 20, effort = 0.5) n <- sim@n[21, , ] n_pp <- sim@n_pp[21, ] getEncounter(params, n, n_pp) }