The Stratified-Petersen Analysis System (SPAS) is designed
to estimate abundance in two-sample capture-recapture experiments
where the capture and recaptures are stratified. This is a generalization
of the simple Lincoln-Petersen estimator.
Strata may be defined in time or in space or both,
and the s strata in which marking takes place
may differ from the t strata in which recoveries take place.
When s=t, SPAS reduces to the method described by
Darroch (1961) < https://www.jstor.org/stable/2332748>.
When shttps://www.jstor.org/stable/2533994>.
Schwarz and Taylor (1998) describe
the use of SPAS in estimating return of salmon stratified by
time and geography.
A related package, BTSPAS, deals with temporal stratification where
a spline is used to model the distribution of the population
over time as it passes the second capture location.
This is the R-version of the (now obsolete) standalone Windows
program available at < http://www.cs.umanitoba.ca/~popan/spas/spas_home.html>.

Stratified Petersen Analysis System in R

Versions and installation

CRAN Download the SPAS package

Github To install the latest development version from Github,
install the newest version of the devtools package; then run

This is an R version of the Windoze program SPAS to estimate population abundance
using a Stratified Petersen Estimator (Darroch 1961; Plante et al 1998; Schwarz and Taylor, 1998)

The user is allows to pool rows and/or columns prior to analysis but the number of rows must be
less than or equal to the number of columns (s <= t). The conditional likelihood formulation of
Plante et al (1998) is used to estimate the parameters.

Because the data are physically pooled prior to analysis, it is not yet possible to compare different
poolings to see which is most appropriate - this is under active investigation. A good discussion
of how to decide on pooling rows/columns is found in Schwarz and Taylor (1998).

References

Darroch, J. N. (1961). The two-sample capture-recapture census when tagging and sampling are stratified. Biometrika, 48, 241–260.
https://www.jstor.org/stable/2332748

Plante, N., L.-P Rivest, and G. Tremblay. (1988). Stratified Capture-Recapture Estimation of the Size of a Closed Population. Biometrics 54, 47-60.
https://www.jstor.org/stable/2533994

Schwarz, C. J., & Taylor, C. G. (1998). The use of the stratified-Petersen estimator in fisheries management with an illustration of estimating the number of pink salmon (Oncorhynchus gorbuscha) that return to spawn in the Fraser River. Canadian Journal of Fisheries and Aquatic Sciences, 55, 281–296.
https://doi.org/10.1139/f97-238

News

SPAS 2018.11.22

First release of conversion of Windoze SPAS to R SPAS