A component of a stock assessment model, made up of formulations that describe how the population changes from one time period to the next. The types of population models vary depending on the species life history and on data availability. Population models can roughly be classified as age/size structured or biomassbased, deterministic or stochastic, density-dependent or density-independent, spatially structured or spatially aggregated, equilibrium or nonequilibrium.

Image Source: Beaudouin R, Goussen B, Piccini B, Augustine S, Devillers J, Brion F, et al. (2015) An Individual-Based Model of Zebrafish Population Dynamics Accounting for Energy Dynamics. PLoS ONE 10(5): e0125841. https://doi.org/10.1371/journal.pone.0125841