1. The rate at which the numbers in a population decrease with time due to various causes. Mortality rates are critical parameters in determining the effects of harvesting strategies on stocks, yields, revenues, etc.
The proportion of the total stock (in numbers) dying each year is called the " annual mortality rate ". To facilitate calculations, scientists express mortality as an exponential rate (called instantaneous rates): Nt/N0 = e-Z = e=(M+F), in which Nt/N0 is the survival rate; M, the natural mortality rate; F, the fishing mortality rate; and Z, the total Mortality rate (deaths due to predation or disease).
See: Annual mortality rate, Instantaneous mortality rate