Age dependence of natural mortality coefficient in fish population dynamics.

From a viewpoint of life history of fish, the natural mortality can be divided into three phases: initial, stable death, and death by senescence, and the respective phases correspond to the three growth phases: early, stable growth, and senescence. According to the relation between natural motality and the growth, a functional formula of the natural mortality coefficient is given in this study. When the von Bertalanffy's growth parameters are known, the natural mortality coefficient can be calculated for each age. As a function of age, the natural mortality coefficient has some general characters throughout the life.