Mark and recapture
A method used to estimate the size of a population. Part of the population is captured, marked and released. Another part of the population is then captured and the number of marked individuals within that sample is counted. An estimate of the size of the total population may then be obtained by dividing the number of marked individuals by the proportion of marked individuals in the second sample. This method, applied at intervals, allows for estimating changes in the size of populations due to reproduction and survival.