capturerecapturemenetelmät

Capture-recapture methods, also known as mark-recapture or sample count methods, are ecological techniques used to estimate the size of a population. These methods involve capturing a sample of individuals from a population, marking them in a way that doesn't harm them, and then releasing them back into the population. After a suitable period, a second sample is taken, and the number of marked individuals in this second sample is recorded.

The fundamental principle behind capture-recapture is that the proportion of marked individuals in the second sample should be representative of the proportion of marked individuals in the entire population. Various formulas exist to estimate population size based on the number of individuals initially captured and marked (M), the total number of individuals captured in the second sample (n), and the number of marked individuals recaptured in the second sample (m). A common estimator is the Lincoln-Petersen index, calculated as N = (M * n) / m, where N represents the estimated population size.

These methods are widely used in wildlife biology, fisheries management, and entomology to estimate populations of animals, fish, and insects. They are particularly useful for mobile or elusive species that are difficult to count directly. However, the accuracy of capture-recapture estimates depends on several assumptions, including that the population is closed (no births, deaths, immigration, or emigration between samples), that marks are not lost or overlooked, and that marked individuals mix randomly with the unmarked population. Violations of these assumptions can lead to biased population estimates.