Oregon state officials are looking into why thousands of fish, including hundreds of trophy-sized trout, died along the banks of the Deschutes River after flows were reduced to begin building water levels in Wickiup Reservoir for next year’s agricultural needs.

A report from Oregon Public Broadcasting (OPB) says local volunteers and Oregon Department of Fish and Wildlife (ODFW) employees moved hundreds of fish a quarter mile from a shrinking pool to the main stem of the river last Friday, but still found over 1,400 rainbow and brown trout, 1,300 sculpins and 1,300 whitefish dead.

The Oregon Water Resources Department says it hasn’t done anything different from previous years that would lead to a fish kill.

“At the end of irrigation season, we’ll drop reservoir outflows down to begin storing water through the storing season throughout the winter,” said Oregon Water Resources Region Manager Kyle Gorman. “Hopefully, somebody will figure out what did happen this year, as to previous years, and then find a solution so it doesn’t happen again.”