Zusammenfassung: A mathematical model which simulates sport-fish production yield and economic value in the Rio Grande basin of New Mexico is described. The model links hydrologic, biologic, and economic components into a mathematical representation of fisheries habitat, fishery dynamics, economic benefits, and income generated by sport-fishing in New Mexico. The model has a research version programmed in FORTRAN. The model users can modify water volume flowing through the basin by month, water stored in each reservoir, water discharged through connecting water material concentrations (suspended solids, total phosphorus, total nitrogen) in the water, site access, and site quality. (Prepared in cooperation with New Mexico State Univ., Las Cruces. Dept. of Fishery and Wildlife Sciences. Sponsored by Geological Survey, Reston, VA (USA). Water Resources Div.)