MICHAEL CAST The upper Clark Fork River cleanup enters a new phase this spring with remediation of a section between Warm Springs and Galen known as Phase 3. As the Montana Department of Environmental Quality and Montana National Resource Damage Program prepare to start construction mid-May, Montana Fish Wildlife & Parks biologists are dealing with a question central to the economic value and health of the river â why has the brown trout population reached all-time lows in the last several years? There is widespread concern that loss of sheltered banks from remediation is a factor. âBasically what we're seeing is that brown trout numbers are down throughout the entire river in both remediated and unmediated sections,â FWP fish biologist Nathan Cook said Wednesday during a Zoom presentation of the panelists in charge of the cleanup.