9458

• UCREFRP Catalog Number: 9458
• Author: National Park Service.
• Title: Workshop on Population Estimates for Colorado Pikeminnow and Humpback Chub.
• USFW Year: 2001.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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MODELS USED:

Schnabel Multiple-Census Population Estimate

The following information was excerpted from Van Den Avyle (1993).

Table 1.

Example data records and calculations for Schnabel multiple-census
population estimate.

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Total
number of
Number of fish captured marked fish
released
prior to
Sample ( t) Marked (R) Unmarked Total (C) sample CXM
period
1 0 150 150 0 0
.
2 22 203 225 150 33,750
3 26 86 112 353 39,536
4 53 150 203 439 89,117
5 38 80 118 589 69,502
6 28 53 81 669 54,189
7 87 150 237 722 171,114
Total 254 457,208

The Schnabel population estimation formula is:

I
I
I
I
I
I
I

^
N=

I ~=lC,M,
I~=lR,

where the subscript t refers to the individual sample period, and n is the
number of periods. For our example,

^
N=

I~=IC,M,
I ~=l R,

OR

^ 457,208
N = 254 = 1,800