Measuring Abundance : Methods for the Estimation of Population Size and Species Richness by Graham J. G. Upton

Author:Graham J. G. Upton
Language: eng
Format: epub
Publisher: Pelagic Publishing

7.1 Capture-recapture models for a closed population

7.1.1 Two trapping occasions

The first use of capture-mark-recapture methods was made by Petersen (1896), who wished to estimate the size of a fish population. The method gained prominence, following its use by Lincoln (1930) to estimate the size of a bird population. Nowadays, the method that they used is variously described as the Petersen mark-recapture estimator, the Lincoln index, the capture-recapture method, or by some variant of these.

On the first occasion, from a population of unknown size, N, a total of n1 individuals are captured, marked, and returned to the population. On the second occasion n2 individuals are trapped and examined. Suppose that m2 of these individuals are found to have been marked. Equating the proportion of marked individuals on the second occasion (m2/n2) to the proportion of marked individuals in the entire population (n1/N) suggests that an estimate of the population size is given by:

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