The model can be termed a switch or survival gauntlet model in that it represents successive conditions or switches that must be realized for the fish to survive. Each switch has a conditional probability of being set for survival or mortality. The probability is subject to spatial and temporal variability.
Switches can act on individuals, cohorts, or populations.
Working conceptual model of eastern Bering Sea walleye pollock survival at different life stages. Relative mortality, important environmental processes and the life stages that they affect are indicated. In our working conceptual model, most mortality takes place in the juvenile life stage, although mortality during the larval life stage could be important in some years. Two factors have been suggested as important mechanisms in regulating eastern Bering Sea pollock year-class strength. Environmental factors enter our model through their impact on spatial overlap.