Which parameter is NOT needed for mark-recapture estimation?
The Lincoln–Petersen estimate requires three counts: M, the number initially marked and released; C, the total number captured on the second occasion; and R, the marked individuals found within that second capture. The number unmarked in the second sample is C − R, so it is not mathematically independent but can help determine C when only marked and unmarked counts are recorded. Population sex ratio is unnecessary for the basic estimator because the marked proportion, not sex composition, drives N ≈ MC/R. Sex ratio becomes relevant only if capture probabilities differ by sex, sampling targets
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 9