Density Estimation by the Modified Jackson's Method

Abstract

In this study it has been assumed that single batches of marked individuals were released and subsequent density estimates were based on samples obtaiend by recapture counts which were then removed from the population. The bias in these estimates was calculated by using both Jackson's positive method and Itô's modified method for simulated populations. This author concludes that Itô's method is more useful than Jackson's under conditions of low mortality and low capture rates, and, further, that the degree of negative bias in both these methods tends to increase with increases in rates of mortality and capture. Itô's method cannot be applied where the density of wild individuals is extremely low vis-a-vis the marked population. In order to minimize this defect the author proposes a method whereby the ratio of marked to unmarked individuals is used in place of the ratio of marked to total individuals. Another method, usable in situations where the number of captured wild individuals remains nearly constant, to ascertain approximately the rates of survival, capture and density of wild population is also proposed. © 1976, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.