Capture-Recapture

Capture-Recapture is a method of estimating the size of a population by taking two captures. In the first capture, all of the population is tagged to allow for their identification within the second capture. The method works on the assumption that the proportion of the population tagged of the population is equal to the proportion of recaptured tagged population of the recaptured population.

This can be represented with the following equation:

$$\frac{n}{N} = \frac{k}{K}$$

Where:

• $n$ is the count of the tagged population
• $N$ is the count of the whole population
• $k$ is the count of the recaptured population that was tagged
• $K$ is the count of the whole recaptured population

This can be rearranged to find the count of the whole population.

$$N = \frac{Kn}{k}$$

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