On the use of linear models in the estimation of the size of a population using capture-recapture data

In the analysis of capture-recapture data it is often assumed that the population is closed and any variability in the expected number of captures between occasions is due to changes in the capture probabilities. However, it is also possible that the catchable population changes in a systematic way between occasions. Here a martingale estimating equation approach is used to extend closed population estimators to models with systematic changes in the population size that may be explained by covariates. The procedure is applied to capture-recapture data collected on a population of mountain pygmy possums (Burramys Parvus) with capture occasions before and after a major bushfire, to examine the effect of the fire on the population size.