Empirical estimates of natural mortality for the Chilean hake (Merluccius gayi):: evaluation of precision

The precision of the natural mortality rate (M) for Chilean hake (Merluccius gayi) is evaluated using empirical models in which a parametric bootstrap resampling method is incorporated. The empirical models of Pauly (Pauly, D., 1980. J. Cons. Int. Explor. Mer. 39(2), 175-192.), Rikhter and Efanov (Rikhter, V.A., Efanov, V.N., 1976. ICNAF Res. Dec. 76/VI/8:12 p.), and Hoening (Hoening, J.M., 1983. Fish. Bull. US, 82(1): 848-902.) were used to estimate M. The model estimates of M were evaluated based on the error in the estimates of the input parameters and the degree of significant differences between males and females. The average of 3000 equally probable and alternative values of M obtained using the models of Pauly and Hoening were similar for males and females. However, these models produced significant differences between sexes only when the error in the estimates of the input parameters was taken into account. There were not significant sexual differences when the prediction error was included in the variance estimation procedure. The ability to determine significant sexual differences is an important aspect which is usually overlooked in evaluating estimates of male and female M obtained from empirical models. (C) 1999 Elsevier Science B.V. All rights reserved.