There are eight ways in which population densities can be estimated. The techniques are: guess, quadrants, transects, mark and recapture, removal trapping, point quarter, and the random pairs method. The guess method is the cheapest and least time consuming method. A guess is made based on one's own observations as to how many individuals there are of the species. The quadrant method uses the complete area of which the complete population is being measured for and is divided into areas that are squares. Transect method take takes the quadrat that are located in a straight line and are counted. Mark and recapture entails capturing the organisms alive, marking them with tags, dye or fin clipping and then returning the organisms back into the area of they were removed from. Another sample is then taken after the organisms are allowed to redistribute. Removal trapping is also known as "catch per unit effort." This method is useful for animal populations that are difficult to mark. Point quarter is used by randomly selecting a point where a quadrat line crosses or forms an intersection. Dirtectes are used to assign the locations using: northeast, northwest, southeast and southwest. Random Pairs methods is similar to the point quarter method, using an intersection of a quadrat and measuring the distance from the closest organism to the intersection to the first organism that can be measured crossing and imaginary line that passes though the intersection at a ninety degree angle.
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