Montana wildlife officials are finding more dead fish on the Yellowstone River and trying to determine if they were killed because of a parasite that prompted a shutdown of the popular waterway last year. Montana Fish Wildlife and Parks said its workers found 19 dead mountain whitefish on Thursday in the Paradise Valley upstream of Livingston. Seventy-nine dead fish, including one trout, had earlier been found downstream of Livingston. The state shut down a 183-mile stretch of the Yellowstone last year after a disease caused by an invasive parasite killed tens of thousands of whitefish. Fisheries manager Travis Horton at FWP Region 3 in Bozeman told CBS affiliate KTVQ that biologists will float from sites upstream of Livingston on Thursday, the same area hit hardest last summer by proliferative kidney disease, or PKD. "We've got staff out floating the river and anticipate we'll know more by the middle of next week," said Horton. "Protecting the health of the river and fishery is our top priority, so we're taking every precaution." Fish, Wildlife and Parks spokesman Greg Lemon says no closures are anticipated this year because the Yellowstone is running colder and higher - conditions that are more favorable for fish.