1. Chapter 8 Estimating Population Size: Capture-Recapture Model Examples: Estimating number of blue whales Estimating number of fish in a lake Estimating deer population

2. Chapter 8 Estimating Population Size: Capture-Recapture Model The Method n = # of animals captured and marked (capture sample size) The captured animals are released into their natural habitat. M = # of animals captured the second time (recapture sample size) m = # of marked animals in recaptured sample

3. Chapter 8 Estimating Population Size: Capture-Recapture Model Basic Idea: Let N denote the unknown population size. Assumption: Proportion of captured animals to total population size should be close to proportion of marked animals in recapture sample. m/M is approximately equal to n/N. Thus (nM)/m is an approximation to N.

4. Chapter 8 Estimating Population Size: Capture-Recapture Model Remarks: 1. If m/M is “small” then N is “large” 2. If m/M is “large” then N is “small”

5. Chapter 8 Estimating Population Size: Capture-Recapture Model Some Assumptions: 1.Each animal has the same chance of being captured before and after marking 2.Enough time is allowed for integration before recapture sample is taken 3.No birth or death 4.No migration 5.Markings stay at least until a recapture sample is taken