POOLED POPULATION PARAMETER ESTIMATES FROM MARK-RECAPTURE DATA

The reduced capture history (RCH), compiled from complete capture hist ories of uniquely marked animals, for a given pooling interval contain s the same information as would be obtained from experiments where (i) a single sample lasts the duration of the pooling interval; (ii) an i dentical batch mark is applied to animals captured in a series of samp les carried out during the pooling interval. For stationary population s, biases are calculated for the RCH estimates of all parameters in th e Jolly-Seber (J-S) model. The results are verified using simulation. The biases are functions of the survival and capture probabilities and the degree of pooling; they are less than 5% for the total population , birth and survival rates, and probability of capture during the pool ing interval if the mortality and capture probabilities do not exceed about 50% per pooling interval. The marked population, marked fraction , and probability of recapture cannot be estimated directly by the RCH method but can be obtained iteratively from the bias formulae. The bi ases in other parameters can be reduced by the same procedure. Alterna tive estimates are derived that are not detectably biased, for any est imate, for mortality and capture probability up to about 60% per pooli ng period. The new estimates have higher sample variances than the RCH estimates, but for large populations with high mortalities and captur e probabilities the difference is small.