Estimates of Historical Surplus Production of Freshwater Fish Populations Across Minnesota, Wisconsin, and South Dakota from 1980-2021

A temperature-dependent surplus production model has been used to estimate the historical productivity of freshwater fish populations. The data utilized in this analysis includes: (1) an index of relative abundance; (2) fishery removals and subsidies from stocking programs; and (3) lake growing degree days. Surplus production represents the net change in population biomass in the absence of fishing, reflecting the interplay of population dynamics such as recruitment (gain), individual fish growth (gain), and natural mortality (loss).