Lake Guntersville Largemouth Bass

  1. A total of 23 fish were caught per hour in the first sample.
  2. The catchability coefficient (q) is estimated to be 0.203 with a 95% confidence interval from 0.043 to 0.364. Thus, it is estimated that approximately 20.3% of the Largemouth Bass (Micropterus salmoides) in the enclosures would be captured with one hour (i.e., one unit) of electrofishing effort. This value is the same as that reported in Maceina et al. (1995).
  3. The initial population size (N0) is estimated to be 110 with a 95% confidence interval from 57 to 164. This value is the same as that reported in Maceina et al. (1995).
  4. One would expect to catch 110×(1-e\(^{0.203}\))×1 = 20.3 fish in the first hour of sampling.
  5. To compute the expected catch for the second sample, one must first reduce the original population size by the number of fish removed with the first sample (i.e., N0-N0×(1-e-q)×1) and then multiply that times (1-e-q)×1. Thus, the expected catch for the second sample is (110-20)×0.184×1 = 16.6 fish.

R Appendix

library(FSA)
library(tidyverse)
d <- data.frame(ct=c(23,12,13,14,9,7),
                ft=rep(1,6)) %>%
  mutate(CPE=ct/ft)
depl1 <- depletion(d$ct,d$ft,method="Leslie",Ricker.mod=TRUE)
summary(depl1)
confint(depl1)

 

Benthic Fish in a Headwater Stream

  1. The probability of capture (p) is estimated to be 0.455 with a 95% confidence interval from 0.363 to 0.547.
  2. The initial population size (N0) is estimated to be 287 with a 95% confidence interval from 255 to 319. This value is the same as that reported in Pritchard et al. (2021).
  3. Capture efficiency is the percentage of the estimated number of Bullhead at the site (287) that were captured in the three electrofishing passes (241) – i.e., \(100\frac{241}{287}\)=84%. This is the same value as reported in Pritchard et al. (2021).
  4. There is sufficient evidence to conclude that the probability of capture differed after the first of the three electrofishing passes (p=0.0217).

R Appendix

ct <- c(138,55,48)
rem1 <- removal(ct)
summary(rem1)
confint(rem1)
M1 <- removal(ct,method="Moran")
S1 <- removal(ct,method="Schnute")
teststat <- 2*(M1$min.nlogLH-S1$min.nlogLH)
pvalue <- pchisq(teststat,df=1,lower.tail=FALSE)