Estimating Population Size Using Lincoln Index - page 3
Keywords: Population Size Lincoln Index
By farahnad on 24/09/2007
Level: A Level (Year 12) / AS Level
Page Number: 3 of 4 pages: 1 2 3 4
in the number of species counted which are only 14.
The percentage of difference =
= 6.64%
Hence, Lincoln Index is highly accurate in estimating the population size with only little difference to the actual value. But in this experiment, the number of the beans taken must be at least 20 to get an accurate calculation which is approximately 10% of the total population.
However, there are some limitations when using Lincoln Index method. Firstly, it is suitable only for small animals which inhabit a limited, well-defined habitat. Secondly, there must be no emigration or immigration from the habitat. Third, enough time must be allowed for the released animal to mingle with the rest of the population depending on how fast the movement of the animals are. Fourth, the method of capture must not alter the habitat so the animals will not move away. Fifth, the marking method must not be harmful to the animals, reduce their chance of survival or affect their behaviour patterns.
Compared to capture-release-recapture method, it is assumed that the area within the quadrat frame is representative of the entire area. However, there is a need to consider the size of the quadrat used. In general, smaller quadrats are more reliable than a larger quadrat, but there are practical considerations which need to be taken into account such as time and size of the study area. The distribution of many species is aggregated. One sample therefore, may be completely unrepresentative of the entire population and calculation of the density based on that sample would be inaccurate. To make the result statistically significant, a large number of samples should be taken, but identifying and counting all the species present in a very large sample can be too time-consuming.
From the comparison above, it can be seen that the situation where the mark-release-recapture method is likely to be suitable are going to be limited while quadrat sampling can be used in variety of situation. On top of this, if a reasonably accurate is to be made, Lincoln Index is more useful as the habitat is well-defined and movement of animals can be controlled. Yet, at least 10% of the released individuals from the first sample must be recaptured in the second sample.
Conclusion:
Using capture-release-recapture method and Lincoln Index is more accurate than random sampling method using quadrat. However, Lincoln Index can be used only in certain situation which is very limited
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