Estimating Population Size Using Lincoln Index - page 1
Keywords: Population Size Lincoln Index
By farahnad on 24/09/2007
Level: A Level (Year 12) / AS Level
Page Number: 1 of 4 pages: 1 2 3 4
Title: Estimating Population Size Using Lincoln Index
Objective: To estimate the population size using Lincoln Index
Background Summary:
The capture-mark-recapture is a technique for estimating the size of a population of organisms. A sample of the population is taken and these organisms are marked in some way so that they can be identified later. They are then released and allowed to disperse into the population. A second sample is then taken and the numbers of marked organisms recaptured, and those captured that are unmarked are recorded. A formula, referred to as the Lincoln Index, is then used to estimate the total population size. There are numbers of important assumptions in this method:
• The mark has no effect on the organisms
• The mark persist during the investigation
• The marked organisms disperse randomly throughout the whole population
• The population is closed, that is no migration of organism
• No birth or death during the investigation
The formula for the Lincoln Index:
N = the estimated total population size
S1 = the number of organisms marked and released
S2 = the number of organisms captured in the second sample
R = the number of marked organisms recaptured
Besides of that, random sampling using a quadrat can also be used to estimate the number of species in one place. A quadrat frame usually made of wood or metal and is used to take a sample of the area under investigation. It would be impractical to count every individual, so instead we need to use sampling technique. Therefore, it is assumed that the area within the quadrat frame is representative of the entire area.
Materials:
• Beans (at least 100 beans)
• Permanent marker pen
• Box
Method:
1. A sample of beans from the population in the box is taken. If there are fewer than 20 beans in this sample, a larger sample is taken. For example, one handful beans.
2. The number of beans in the sample [S1] is counted and recorded, and each one is marked with a coloured dot.
3. The beans are returned into the box and the box is shaken so that the beans will be mixed randomly.
4. A second sample is taken, and the total number of the beans present in this sample [S2] and the number of these which are marked [R] are noted and recorded.
5. The Lincoln Index is used to calculate the estimated population size from the results gained.
6. The actual number of beans present in the population is then counted.
Results:
Sample / n 1 2 3
S1 53 69 74
S2 41 70 73
R 11 21 22
N 198 230 246
M = total amount of population
M = 211
N1 =
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