Ruffe Extirpation Experiment

Czypinski and Ogle (2011) performed an experiment to determine if a population of invasive Ruffe (Gymnocephalus cernuus) could be significantly reduced by sequential removal of Ruffe with bottom trawls. At the Kakagon River location the following catches of Ruffe were made with the corresponding minutes of trawling effort.

Catch   282  346   37    4    9   27    4    0    1    0
Effort 19.0 30.0 31.0 20.0 29.5 42.5 34.5 36.0 27.0 25.0
  1. Enter the catch and effort data into separate R vectors, convert the effort vector to hours of trawling, and calculate a vector that represents the CPE in each sampling period. Carefully interpret the meaning of the first value in the CPE vector.
  2. What is the best estimate and 95% confidence interval for the catchability coefficient? Very carefully interpret what this estimate means relative to the capture of Ruffe at this site.
  3. Convert the estimated of catchability to a quantity that is more easily interpretable. Interpret that quantity.
  4. What is the best estimate and 95% confidence interval for the initial population size?
  5. What is the best estimate for the percentage of the Ruffe population that was removed with trawling?

 

Signal Crayfish Abundance

Chadwick et al. (2020) 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.

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