Markedsspredning

**Markedsspredning** (also known as **mark-and-recapture** or **capture-recapture**) is a statistical method used in ecology and wildlife management to estimate population sizes of animals, fish, or other organisms. The technique relies on capturing a sample of individuals, marking them in a way that does not affect their survival or behavior, and then releasing them back into the population. Later, another sample is captured, and the proportion of marked individuals in this second sample is compared to the initial marked population to estimate the total size.

The method assumes several key conditions: the population is closed (no births, deaths, immigration, or emigration during the study period), marked individuals mix uniformly with the unmarked population, and the marking does not influence survival or movement. Common marking techniques include ear tags, radio collars, or visible ear notches for small mammals. The most widely used formula for estimating population size is the **Lincoln-Petersen estimator**, derived from the ratio of marked to unmarked individuals in the second sample.

While markedsspredning is straightforward, its accuracy depends on careful implementation. Factors such as movement patterns, habitat fragmentation, and seasonal changes can introduce bias. Alternative methods, like mark-recapture with multiple recaptures or distance sampling, may be used for more complex scenarios. Despite its limitations, markedsspredning remains a valuable tool in ecological research, conservation biology, and fisheries science.