A General Cohort Analysis Method

A general cohort analysis method for exploited wildlife populations is described and analysed. Basic mathematical properties are studied for the case of deterministic, Riemann-time-integrable mortality rates, and differentiable cumulative catch function, and a simple, but still flexible, technique for stepwise backcalculation of a cohort is given as a special case. It is shown, and illustrated by examples, that this may replace existing virtual population analysis techniques, and even give better estimates, when existing techniques are biased. Expressions for the sensitivity of backcalculated cohort numbers and mean exploitation rates to simultaneous deviations in input parameters and functions are derived analytically, and some properties of these expressions are demonstrated in examples.