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Calculate fisheries productivity for each species group

getProductivity.Rd

This function calculates the total potential fisheries productivity by species group in a given size range using species abundances and the getEGrowthTime() function.

Usage

getProductivity(
  object,
  time_range = NULL,
  include_repro = FALSE,
  min_fishing_l = NULL,
  max_fishing_l = NULL,
  ...
)

Arguments

object

An object of class MizerParams or MizerSim. If given a MizerSim object, uses the growth rates at the final time of a simulation to calculate productivity. If given a MizerParams object, uses the initial growth rates.

time_range

The time range (either a vector of values, a vector of min and max time, or a single value) to provide productivity for. Default is the final time step. Ignored when called with a MizerParams object.

include_repro

A boolean value that indicates whether to include energy for reproduction in productivity estimates. Defaults to using getEGrowthTime() if FALSE or mizer's mizer::getEReproAndGrowth() if TRUE.

min_fishing_l

The minimum length (cm) of fished individuals for productivity estimates. Defaults to 7 cm.

max_fishing_l

The maximum length (cm) of fished individuals for productivity estimates. Defaults to max length.

...

Arguments passed on to mizer::get_size_range_array

params

MizerParams object

min_w

Smallest weight in size range. Defaults to smallest weight in the model.

max_w

Largest weight in size range. Defaults to largest weight in the model.

min_l

Smallest length in size range. If supplied, this takes precedence over min_w.

max_l

Largest length in size range. If supplied, this takes precedence over max_w.

Value

If called with a MizerParams object, a vector with the productivity in \(\frac{grams}{m^2}/year\) for each species group in the model. If called with a MizerSim object, an array (time x species) containing the total productivity at each time step for each species.

Potential fisheries productivity

Productivity refers to the rate at which fish biomass is produced and available for harvest in a given area over a given period of time. Productivity cannot be measured in situ.

The productivity \(P_i(w)\) of species group \(i\) is given by

$$P_i(w) = \int_w^{w+dw} \left( N_i(w) + g_i(w) \right) w \, dw.$$

\(N_i(w)\) is the abundance density \((no./m^{2})\) and \(g_i(w)\) is the energy rate available for growth after metabolism and movement have been accounted for \((grams/year)\). The productivity is calculated for all fish in the size range between min_fishing_length and max_fishing_length. These lengths can be the same for all groups or can be specified as a vector with one value for each species in the model. The minimum length defaults to \(7 cm\) regardless of species group and maximum length defaults to the maximum weight in the model.

See also

getEGrowthTime(),plotProductivity()