Measuring Populations (4)

Sampling non-motile populations (4)

• Random sampling

• Systematic sampling

• Transect sampling

• Quadrat sampling

Random sampling

• gives every individual in the population an equal chance of selection

• eliminate bias

• not representative of a whole population

Systematic Sampling

• collecting samples at certain intervals, in a regular pattern

• easy to use, and is more likely than random sampling to be representative where an environmental gradient is present

• possibility for biases —> inadvertently create unrepresentative patterns of information

Transect sampling

marking a transect line through a habitat that you want to observe. This could be done with chalk, tape, string or using other methods. You then collect data along the transect line. If you collect samples at certain intervals along the transect line

Quadrat sampling

Quadrats are square frames used to describe the area of study. Quadrat sampling can be used to estimate: population abundance, population density, percentage cover, and percentage frequency.

Sampling motile populations

• Motile populations cannot be easily sampled.

• Use capture-mark-release-recapture

capture-mark-release-recapture (1)

capture-mark-release-recapture - The Lincoln Index

A formula used to estimate the size of entire population

Limitations to CMRR (4)

• there is a complete mixing within the population before and after the first capture

• the marks have not disappeared

• the marks are not harmful and do not affect the survival of the individual

• there is equal opportunity to catch every individual

• there is no immigration, emigration, birth or death between the two sampling times