Fish Population Dynamic and Stock Assessment

1.1.3. Population dynamics

Population dynamics is a branch of life science which is concerned with the short and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes. It deals with the way populations are affected by birth and death rates, and by immigration and emigration, and studies topics such as ageing populations or population decline.

Population dynamics has traditionally been the dominant branch of mathematical biology, which has a history of more than 210 years, although more recently the scope of mathematical biology has greatly expanded. The first principle of population dynamics is widely regarded as the exponential law of Malthus, as modelled by the Malthusian growth model.

A more general model formulation was proposed by F.J. Richards in 1959, further expanded by Simon Hopkins, in which the models of Gompertz, Verhulst and also Ludwig von Bertalanffy are covered as special cases of the general formulation. The Lotka-Volterra predator-prey equations are another famous example. The best mathematical model that governs the population dynamics of any given species is called the exponential model.

In fisheries and wildlife management, population is affected by three dynamic rate functions, such as Natality or birth rate, population growth rate and mortality rate.