Abundance from Removal Data

Chequamegon Bay Ruffe

Estimate abundance of Signal Crayfish in Bookill Gill Beck captured with an experimental method.
Invasive Species

Derek H. Ogle


Dec 23, 2022


Feb 13, 2023

Chadwick et al. (2021) examined a novel method to determine the abundance of Signal Crayfish (Pacifastacus leniusculus) in an isolated portion of a stream. At one experimental location their novel method resulted in the removal of 1477, 133, and 46 crayfish in three successive samplings. Use these data to answer the following questions.

  1. What is the best estimate and 95% confidence interval for the population size?
  2. What is the best estimate and 95% confidence interval for the probability of capture for each sampling period.
  3. Is there evidence that the probability of capture differed after the first pass?


Solution Code:

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Chadwick, D. D. A., E. G. Pritchard, P. Bradley, C. D. Sayer, M. A. Chadwick, L. J. B. Eagle, and J. C. Axmacher. 2021. A novel “triple drawdown” method highlights deficiencies in invasive alien crayfish survey and control techniques. Journal of Applied Ecology 58:316–326.