Estimation of instantaneous rate of natural mortality from catch-at-age data and an abundance index based on extended survivors method

This study utilized the catch-at-age data and an abundance index (catch per unit effort, CPUE) to estimate instantaneous rate of natural mortality (M) of fish by using the extended survivors method. In generating the artificial data, two alternative assumptions of constant and varied catchability were made. Monte Carlo simulations showed that the estimates of M were more sensitive to the coefficient of variation (CV) in the catch data. Smaller instantaneous rate of fishing mortality (F) or large M could improve the estimates of M, but which are more sensitive to F. The method was also applied to two sets of published data, and both obtained viable estimates of M.