abundance estimates in robust design with closed captures

[dianeja_]

Hi,
I`m using the closed captures module in the robust design in Mark to estimate population size in voles.

For some of the primary occasions the estimated abundaces are lower than the number of unique captured animals, which does not make sense. What can this artefact might be due to?

(In case it might help, I fixed P=C, and I got pretty high values P=C=0.71)

Thank you very much for your answer and help,
Diana