depletM {fishmethods}R Documentation

Catch-Effort Depletion Methods Incorporating Natural Mortality

Description

Following Rosenberg et al. (1990), the Leslie-Davis and catch equation depletion methods that incorporate natural mortality are implemented for a single fleet. Initial population size (N0) and catchability coefficients with standard errors are estimated from cpue and catch, respectively, via multiple linear regression (Leslie-Davis) and nonlinear regression (catch equation).

Usage

depletM(catch = NULL, effort = NULL, M = NULL, 
 method = c("l", "c"),stq = NULL, stN0 = NULL)

Arguments

catch the vector containing catches for each removal period (in sequential order).
effort the vector containing effort associated with catch for each removal period. Rows must match those of catch.
M the constant natural mortality rate
method the depletion method: l=Leslie-Davis, c=catch equation. Default is both.
stq initial guess for catchability if the catch equation method is used.
stN0 initial guess for N0 if the catch equation method is used.

Details

For the Leslie-Davis method, cpue is calculated internally from catch and effort. The natural mortality rate must be scaled to time period between removal (see Rosenberg et al. (1990) for more details). The lm and nls functions are the estimation methods for the Leslie-Davis and catch equations, respectively.

Value

results list element containing a table of parameters, estimates, associated standard errors, and confidence intervals for each method
outpt list element containing the calculated regressors, predicted cpue (Leslie) or catch (catch equation) and residuals

Author(s)

Gary A. Nelson, Massachusetts Division of Marine Fisheries gary.nelson@state.ma.us

References

Rosenberg, A.A., G. P. Kirkwood, J. A. Crombie, and J. R. Beddington. 1990. The assessment of stocks of annual squid species. Fish. Res. 335-350.


[Package fishmethods version 0.0-1 Index]