Both versions of synthesis allow inclusion and estimation of spawner-recruitment functions. When detailed age composition data are lacking, the estimated spawner-recruitment curve can be used to generate the entire time series of recruitments, thus turning synthesis into a simple production model. At the other extreme, inclusion of the spawner-recruitment curve in data-rich models allows estimation of this curve while taking into account all available information. Although most population modeling is done within unit stocks, age synthesis provides the capability to model up to three geographic areas and to estimate the degree of migration between areas. Size synthesis adds a body size dimension to the.
