calcRealCatch: Calculate realized catches

In CamFreshwater/samSim: Closed-loop salmon dynamics simulator

Calculate realized catches

Description

This function calculates realized catch based on beta distributed outcome uncertainty.

Usage

calcRealCatch(rec, tac, sigma = 0.1, random = FALSE, setSeedInput = NULL)

Arguments

rec	A numeric vector of length nCU representing CU-specific recruitment.
tac	A numeric vector of length nCU representing CU-specific target total allowable catch rates (generally passed from calcTAC function).
sigma	A numeric representing the standard deviation of the shape parameter.
random	A logical (default 'FALSE') used to restandardize random number generator because 'rbeta()' seems to produce variable draws (should be corrected in future).
setSeedInput	A numeric representing the combination MC trial and simulation year to ensure that scenarios are sampling the seed, but allowing draws to otherwise vary.

Details

Outcome uncertainty is often easier to parameterize using observed deviations in target and realized exploitation rates rather than catches. Here target total allowable catches are back-converted to exploitation rates and realized catches are generated using beta distributed outcome uncertainty (as in Anderson et al. 2015 J. App. Ecol.).

For simplicity's sake when TAC is zero, realized HR is zero. Therefore to represent "significant" catch even when TAC is zero, pass large sigma values and a small, non-zero TAC value.

**Note** the sigma values representing the standard deviation of the shape parameter for the beta distribution are **not** equivalent to the SD of a normal distribution. Values larger than ~0.2 can result in U-shaped realized exploitation rates. Distribution should be parameterized based on data or use default value (0.1) from Pestes et al. 2008 for Cultus Lake sockeye salmon.

**Note** small target harvest rates and/or high sigmas can produce negative location parameters which result in NAs; replace with small values (see betaDistributionBounds.Rmd for details) .

Value

Returns a vector of length nCU representing realized catches

Examples

head(exampleHCRList)
exRec <- exampleHCRList$recRY
exTAC <- 0.2 * exRec
calcRealCatch(exRec, exTAC, sigma = 0.1)

CamFreshwater/samSim documentation built on Sept. 25, 2023, 10:22 a.m.