Investigating populations

What is abundance?

The number of individuals of a species within a given area

When is mark-release-recapture techniques used?

For motile animals- may move away when approached

How does mark-release-recapture work?

A known number of animals are caught, marked and then released. Some time later, a given number is collected randomly and the number of marked is recorded.

How to work out the estimated population size?

Total number of individuals in first sample x total number of individuals in the second sample / number of marked individuals recaptured

Where are the assumptions for mark-release-recapture?

The proportion of marked to unmarked individuals in the 2nd sample is the same as the proportion of marked to unmarked individuals in the population as a whole

The marked individuals released from the first sample distribute themselves evenly amongst the rest of the population and have sufficient time to do so

The population has a definite boundary so there’s no immigration or emigration

There are few births or deaths

The method of marking is not toxic to the individual nor does it make them more liable to predation

The mark or label is not lost or rubbed off during the investigation

The size of a population can be estimated using what?

Randomly placed quadrats, or quadrats along a belt transect, for slow moving or non motile organisms

Mark-release-recapture