Farmers produce many things in abundance for which they receive income, including food, feed, fiber and fuel. Similarly, farmers generate environmental benefits such as improved water quality by reducing soil and nutrient loss and improved wildlife habitat by managing their operation in certain ways. Unfortunately, most farmers receive limited or no compensation for these positive externalities they produce. If we wish to encourage more of these positive externalities, policies need to be established and implemented that compensate producers for the benefits society receives from specific farming practices. This research examined how production practices that provide environmental benefits would affect water quality (nutrient and sediment loss), fisheries populations, and farm income in two distinct study areas in Minnesota. We developed a computer simulation model to examine the relationship between agricultural practices, water quality, fish communities, and net farm income within two small watersheds. Our analyses focused on a coolwater stream, the Wells Creek watershed in southeastern Minnesota, and a warmwater stream, a sub-watershed of the Chippewa River in western Minnesota. We used the Agricultural Drainage and Pesticide Transport (ADAPT) model in relation to land use to calculate in-stream suspended sediment concentrations using estimates of sediment delivery, runoff, baseflow and stream bank erosion, and quantified the effects of suspended sediment exposure on fish communities. Our focus was to estimate how agricultural Best Management Practices (BMPs ? conservation tillage and nutrient management implemented on all cropland, and 100 foot grass buffers along streams) would affect stream fish communities and net farm income, with reference to current conditions. We found a decrease in "lethal" concentrations of suspended sediment on fish in Wells Creek watershed with an increase in conservation tillage, riparian buffers, and permanent vegetative cover. However, land use change in the Chippewa River watershed did not significantly decrease the effects of suspended sediment on the fish community. This difference between watersheds is likely due to differential tolerance to suspended sediment between coolwater and warmwater fish communities and differences in topography, runoff and bank erosion between the two streams.