A legacy of metals mining has historically impaired the ecological health of the Clark Fork Basin (Montana, USA). Since the Superfund designation in 1983, large stretches of the Clark Fork River and its tributaries have been restored, leading to improvements in water quality and fish populations. However, in the last decade, nearly all three-year-old or younger brown trout have been absent from the uppermost reaches of the Clark Fork River. This decline in population was coincident with many changes to the management of mine waste, including the start of a new discharge of treated mine-wastewater. When this mine-wastewater is discharged, it enriches the river with a mixture of solutes that may alter metal toxicity or induce new risks to fish populations. We evaluated flow-normalized trends in metal(loid) (arsenic, cadmium, copper, lead, zinc) concentrations and loads across four sites in the Clark Fork Basin with varying degrees of restoration, exposure to active and historical mine wastes, and fish population histories using the Weighted Regressions on Time, Discharge, and Season (WRTDS) model. Preliminary results suggest that annual average concentrations of most metal(loid)s have declined over nearly 30 years, with the largest declines at restored sites and smallest declines at unrestored sites. Additional analyses will evaluate risks associated with recent metal(loid) concentrations, such as trends in metal bioavailability during periods when fish populations are vulnerable (e.g., May and June for juvenile brown trout). These results will help better understand if fish populations in the Clark Fork River are still affected by historic or active mining mitigation activities or other factors.