Z_CPUE function

Estimate Z from CPUE data

Method to estimate the instantaneous total mortality rate (Z) from catch per unit of effort (CPUE) data according to standard, Heincke's, or Robson & Chapman's method.

Z_CPUE(param, method = "standard", omit_age1 = FALSE)

Arguments

• param: a list consisting of following parameters:

  • cohort: a vector with with a cohort label,
  • age: a vector with ages,
  • CPUE: a vector with CPUE values;

• method: a character string indicating which assessment method should be used: "standard", "Heincke", or "RobsonChapman".

• omit_age1: logical; if TRUE the first age group is omitted (Default FALSE).

Returns

A list with input parameters and a Z value or matrix depending on the method.

Details

In Heincke's and RobsonChapman's method age groups older than 4 are lumped, because age groups older than 3 or 4 are said to be hard to seperate (Ricker, 1975). Sparre and Venema (1998) recommend to omit the first age group in case it is not fully exploited by the fishery.

Examples

# load data
data(synCPUE)

# run model with standard method
Z_CPUE(synCPUE, method = "standard")

# run model with Heincke's method
Z_CPUE(synCPUE, method = "Heincke")

# run model with Robson and Chapman's method
Z_CPUE(synCPUE, method = "RobsonChapman", omit_age1 = TRUE)

References

Sparre, P., Venema, S.C., 1998. Introduction to tropical fish stock assessment. Part 1. Manual. FAO Fisheries Technical Paper, (306.1, Rev. 2). 407 p.

Sparre, P., Venema, S.C., 1999. Introduction to tropical fish stock assessment. Part 2. Excercises. FAO Fisheries Technical Paper, (306.2, Rev. 2). 94 p.

Ricker, W.E., 1975. Computation and interpretation of biological statistics of fish populations. Bull.Fish.Res.Board Can., (191):382 p.