Fish Population Estimate Calculator

Estimate fish population size using the Lincoln-Petersen mark-recapture method with Chapman correction and 95% confidence intervals.

Marked & released (M)

Second capture (C)

Recaptured (R)

Survey area (hectares)

Tab to move between fields

Estimated population (N̂)

743

95% CI lower bound373

95% CI upper bound1,112

Standard error188.4

Density (fish/ha)74.3

Recapture rate (%)12.5

How to Use This Calculator

Enter the number of fish captured and marked in the first sampling event (M).
Input the number captured in the second event (C) and the number of recaptures (R).
Review the Lincoln-Petersen population estimate: N = (M × C) / R.
Check the confidence interval — the estimate is unreliable if recapture rate R/C is below 0.05.
Use the Chapman modification for small samples to reduce bias in the estimator.

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