Estimating Population Size

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Estimating Population Size
BEFORE YOU START

1. What are the AIMS of your study?
2. Do you need ABSOLUTE numbers?
3. Understand the BIOLOGY of your study organism
4. CENSUS or SAMPLE?
5. Reliability of data
6. Bias in data OPERATIONAL and STATISTICAL
7. Costs..

2
Decision tree to assist you decide which methods
to use when estimating population size/s (from
Krebs, 1999)
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Mark Recapture Methods.

1. Is marking necessary?
2. Is the population open or closed?

Basic Equation
M No Caught at t0 C No Caught at t1 R No
caught at t1, marked at t0 N Estimate of
population size
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ASSUMPTIONS Peterson Method

1. Population is closed (make t1-t0 short not too
   short)
2. ALL individuals have same chance of capture
3. Marking does not affect catchability
4. Animals dont lose marks between capture events
5. ALL marks are reported
6. Sampling is RANDOM

5
Decision tree to help you determine the correct
method of calculating 95 CI.