ep_growth: Fitting the von Bertalanffy growth model to length-stratified...

In fishmethods: Fishery Science Methods and Models

Fitting the von Bertalanffy growth model to length-stratified age samples

Description

Estimation of von Bertanffy growth parameters based on length-stratified age samples (Perrault et al., 2020)

Usage

ep_growth(len=NULL,age=NULL,Nh=NULL,nh=NULL,starts=list(Linf=60,
k=0.1,a0=-0.01,CV=0.5), 
bin_size=2,nlminb.control=list(eval.max=5000, 
iter.max=5000,trace=10),
tmb.control=list(maxit=5000,trace=FALSE),plot=TRUE)

Arguments

len	vector of lengths.
age	the vector of ages associated with the length vector.
Nh	the total sample size per bin. Includes the unaged fish.
nh	the total aged sample size per bin.
starts	the starting values for L-infinity, K, a0 and CV. Required.
bin_size	the bin size (e.g., 2 for 2-cm) of the length stratification.
nlminb.control	controls for the nlminb function. See function nlminb for more information.
tmb.control	controls for the TMB function. See package TMB for more information.
plot	plot observed and model predicted lengths at age. Default is TRUE.

Details

The von Bertalanffy growth model Lage=Linf*(1-exp(-K*(age-a0)) is fitted to length-at-age data collected via length-stratified sampling following the EP method of Perreault et al. (2020). A plot of model fit is generated unless plot=FALSE.

Value

List containing list elements of the model convergence, parameter estimates and predicted values.

Author(s)

Andrea Perrault, Marine Institute of Memorial University of Newfoundland

[e-mail]

References

Perrault, A. M. J., N. Zhang and Noel G. Cadigan. 2020. Estimation of growth parameters based on length-stratified age samples. Canadian Journal of Fisheries and Aquatic Sciences 77: 439-450.

Examples

 ## Not run: 
	data(ep.data)
	ep_growth(len=ep.data$length, age=ep.data$age, Nh=ep.data$Nh, nh=ep.data$nh,
        starts=list(Linf=60,
        k=0.1, CV=0.5 ,a0=-0.01), bin_size=2,
          nlminb.control=list(eval.max=5000, iter.max=5000, trace=10), 
          tmb.control=list(maxit=5000, trace=F),plot=TRUE)
 
## End(Not run)

fishmethods documentation built on April 27, 2023, 9:10 a.m.