Copyright © University of Cambridge. All rights reserved.

'Counting Fish' printed from

Show menu

Image (c)

I need a figure for the fish population in a lake.

I catch 40 fish and mark a scale on each fish so that they can be identified if caught again.

The fish are then released and one week later I once more catch 40 fish and look to see which of these I caught before.

How does this help me come up with a figure for the fish population in a lake?

What assumptions does this method of estimating the fish population rely on?
How do you think you could improve the accuracy of your estimate?

Click here for a poster of this problem.