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>.
Stratified Petersen Analysis System in R
CRAN Download the SPAS package
Github To install the latest development version from Github, install the newest version of the devtools package; then run
devtools::install_github("cschwarz-stat-sfu-ca/SPAS", dependencies = TRUE, build_vignettes = TRUE)
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).
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