capturerecaptureteknikker

Capture-recapture techniques, also known as mark-recapture or removal methods, are a set of statistical methods used in ecology and biology to estimate the size of a population. These techniques involve capturing a sample of individuals from a population, marking them in some way, releasing them back into the population, and then capturing a second sample at a later time. The ratio of marked to unmarked individuals in the second sample is then used to estimate the total population size.

The simplest and most common method is the Lincoln-Petersen index. In this method, a population is sampled once and individuals are marked and released. A second sample is taken later, and the number of marked individuals recaptured is recorded. The formula for the Lincoln-Petersen index is N = (M * n) / m, where N is the estimated population size, M is the number of individuals initially marked and released, n is the total number of individuals captured in the second sample, and m is the number of marked individuals recaptured in the second sample.

More complex methods exist to account for factors like population changes (births, deaths, immigration, emigration) between samples, unequal catchability of individuals, and mortality or tag loss due to marking. These include the Schnabel method, the Jolly-Seber model, and various removal methods. The choice of technique depends on the specific ecological context, the species being studied, and the assumptions that can be reasonably made about the population and sampling process.

Capture-recapture methods are widely applied in wildlife management, fisheries science, and conservation biology to assess population status, monitor trends, and inform management decisions. They are essential tools for understanding and managing populations when direct counting is impossible or impractical.