The Collie-Sissenwine
Analysis (CSA) model is a stage-based model that
estimates the abundance of two classes, defined as recruits and
post-recruits. Recruits are assumed to become fully available for the
fishery over the model's unit time step. The model requires
indices of abundance for these two stages and estimates of the total
number of animals removed via the fishery.
The model provides estimates of both abundance and mortality
rates. The user can flexibly specify alternative hypotheses regarding
process error and observation error, including models that use process
error only or observation error only. The underlying error
structure for observation and process error can be specified as either
normal and lognormal. If lognormal error is specified the user can
choose whether or not to use bias correction methods.
Bootstrapping can be based on either randomly resampling
from the set of original error terms or by generating random
errors from a parametric distribution with parameters derived from the
original set of errors.
The graphical user interface has full features for model
specification, review, and visualization.
The calculation engine is based on an adaptation of previous
implementations of the model including DELPOP8
by Dr. Jeremy S. Collie at the University of Rhode Island, an APL
version by Dr. Ramon Conser at NMFS Southwest Science Center, La Jolla,
CA, and by various specific versions developed by the Population
Dynamics branch at NMFS Northeast Science Center, Woods Hole, MA.
The input format has been revised and enhanced. All
former input files are converted automatically to the new format.
CSA
has been updated to remove the time of the survey from the
process equation when an exact solution of the catch equation is
selected for either the observed error only or process &
observed error cases. After review, it was concluded that the
time of survey can not be adequately handled in the process equations
as the model is presently designed. Users should adjust catch
data to be on a consistent time interval with the survey indices
entered. Users should enter zero for both time of catch and
time of survey. If users are using the Pope's approximation,
then this change is not affected.
A
new feature has been added for bootstrapping which allows
users to drop from the bootstrap realizations cases where the fishing
mortality is infeasible.
Additionally,
there were changes to the output report to echo
input values not previously reported.
CSA Version 3.01 (March 2005)
Added a new enhancement that incorporates an exact
solution of the
catch equation into both the observed and process & observed
error models. The Pope approximation is available for
comparison with earlier models.
A
bug was fixed that now allows users to
constrain upper & lower limits on catchability.
Collie-Sissenwine
Analysis