(CSA) model (sometimes called catch-survey analysis or the DeLury
model) is a relatively simple two-stage stock assessment model that
abundance, fishing mortality and recruitment using total catch numbers and
data (Collie and Sissenwine 1983; Conser 1995).The “recruit” stage group consists of animals that recruit at, just
before, or during the current time step.The rest of the population comprises the “post-recruit” stage
group.The two stages may
age groups, length groups or any other natural division (e.g. genders in
groups are assumed fully available to the fishery but this assumption can
relaxed in practice if fishing mortality rates are viewed as rates for
CSA (Version 4) was updated during 2013 and previous
versions are no longer supported.The
uses maximum likelihood rather than weighted sums of squares to estimate
parameters.The user must
and year specific CVs that measure the precision of survey observations in
version uses Baranov’s catch equation exclusively to simulate the
approximation is no
longer available because accuracy of the approximation degrades at high
mortality rates.As in
versions, natural morality in each year is specified by the user and not
estimable in the model.The
model does not allow for estimation of process errors.Process errors tend to be difficult to
estimate because they are typically aliased (cannot be distinguished from)
varying survey variances, natural mortality, recruitment and selectivity
parameters already in the CSA model. Multiple surveys and survey types are
allowed, with time of the year that each survey occurred required.
The calculation engine is written in AD Model Builder.
program is based on previous implementations DELPOP8 by Dr. Jeremy Collie
the University of Rhode Island, an APL version by Dr. Ramon Conser retired
SWFSC, and Fortran versions developed by the Population Dynamics Branch at
Completely new version
of CSA written in ADMB. New features include ability to use multiple
different types, the timing within the year of each survey is required,
uncertainty associated with each survey observation is required, and
process error estimation.
CSA Version 3.1.1 (October 2008)
Program fix for calculations when the number of completed iterations
does not equal the number of requested iterations. Prior version
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
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.
new feature has been added for bootstrapping which allows
users to drop from the bootstrap realizations cases where the
mortality is infeasible.
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.
bug was fixed that now allows users to
constrain upper & lower limits on catchability.