ESTIMATING POPULATION-SIZE FROM A CAPTURE RECAPTURE EXPERIMENT WITH KNOWN REMOVALS

We use martingale theory and a method of moments technique to derive a class of estimators for the size of a closed population in a capture-recapture experiment with known removals in either discrete or continuous time. The capture probabilities may vary on each successive capture occasion. Some of the estimators and their associated standard errors have explicit expressions. Optimal estimators in the sense of giving tightest asymptotic confidence intervals for the population size in either cases are also found. Asymptotic results are readily obtained by an application of a martingale central limit theorem. In contrast to previously proposed estimation procedures the present approach requires only a modest amount of calculation and is based on less restrictive assumptions. An example and a small simulation study showed that the proposed estimators perform better than the existing ones. © 1991.