Observations

  1. The initial N can be reliably estimated only if the assumption violation is that there is mortality on both marked and unmarked fish.
  2. The final N can be reliably estimated when the assumption violations are mortality on unmarked fish only or recruitment into the population.
  3. There is no assumption violation that allows both the initial and final populations to be reliably estimated.
  4. The following things should be done to minimize assumption violations:
    1. The marking and recapture run should be relatively close in time to minimize mortality, recruitment, emigration, and immigration.
    2. Technicians must pay attention so that all marked fish that are captured are observed and so that marks/tags are properly affixed.
    3. Steps should be taken to assure that the marked fish mix into the population as a whole (so don’t release fish next to the net).
    4. Marks/Tags and the handling of fish should have as little affect on the behavior and survival of the fish as possible (i.e., handle them quickly and carefully).
# A tibble: 9 x 3
  Situation            N_Initial N_Final
  <chr>                <chr>     <chr>  
1 Lose mark            Over      Over   
2 Mortality (same)     OK        Over   
3 Mortality (Marked)   Over      Over   
4 Mortality (Unmarked) Under     OK     
5 Recruitment          Over      OK     
6 Trap Happy           Under     Under  
7 Trap Shy             Over      Over   
8 Missed Mark          Over      Over   
9 Released Near Net    Under     Under

Lake Huron Sea Lamprey

The population estimates appears to match that of Begstedt et al. at 639 thousand fish. The confidence intervals are not the same as the Poisson method was used here but not in their paper.

R Code and Results

> library(FSA)
## FSA v0.9.1.9000. See citation('FSA') if used in publication.
## Run fishR() for related website and fishR('IFAR') for related book.
> mr1 <- mrClosed(M=555,n=47154,m=40,method="Chapman")
> cbind(summary(mr1),confint(mr1,verbose=TRUE))
The Poisson (exact method) distribution was used.
          N 95% LCI 95% UCI
[1,] 639467  472666  886450