Three weeks later the team repeated the survey. Of 80 recaptured fish, only 5 were marked, suggesting the marked-to-unmarked ratio has changed.
Which assumption of mark-recapture, if violated, could best explain the higher estimate?
- A
Predation only removes unmarked fish.
- B
The number of marked fish must equal the number recaptured.
- Ccheck_circle
Marked individuals mix randomly with the population (immigration may have added unmarked fish).
- D
All individuals are equally likely to be born.
Explanation
Mark-recapture assumes a closed, well-mixed population. Immigration (or marked-fish emigration) would lower the proportion of marked recaptures, inflating the estimate.