Estimating the size of an open population using sparse capture–recapture data

Summary Sparse capture–recapture data from open populations are difficult to analyze using currently available frequentist statistical methods. However, in closed capture–recapture experiments, the Chao sparse estimator (Chao, 1989, Biometrics 45 , 427–438) may be used to estimate population sizes when there are few recaptures. Here, we extend the Chao (1989) closed population size estimator to the open population setting by using linear regression and extrapolation techniques. We conduct a small simulation study and apply the models to several sparse capture–recapture data sets.