Methods of Population Estimation

i) Capture - recapture method
ii) Line transect/ Belt transect/ Quadrat

Explanation

Capture-recapture method is a statistical technique used in ecology to estimate the size of a population of organisms in a particular area. It is often used for animals such as fish, rodents, arthropods and birds. In the first phase, a sample of the population is captured, marked, and then released back into the environment unharmed. After sometime, the same area is sampled again and the total number caught during the second catch is recorded. The number of marked ones in the second capture is also recorded. If:
- The number of fish caught and marked in the first phase is A
- The total number in the second phase be B
- The number of marked fish in the second phase is C
The total number of fish (T) can be calculated as: T = (A * B) / C

In Line transect/ Belt transect/ Quadrat method: 1. Line transect: A string or rope is stretched along across the area in which all the plants (blackjack) touched are counted.
Belt transect: Two line transects are set parallel to each other to enclose a strip. The number of blackjack within the belt is counted and recorded.
Quadrat: A quadrat is a square or rectangular sampling frame used in ecology to study and estimate the population of plants or organisms within a specific area. The number of blackjack found within the quadrat is counted and recorded.

Read on Sampling Methods (Ecology)