GREAT FALLS, Mont. (AP) — State fisheries biologists plan to test fish in the Missouri and Smith rivers for a parasite that killed thousands of fish and led to the temporary closure of the Yellowstone River.

Fish, Wildlife and Parks fisheries manager Grant Grisak says the testing is precautionary.

Beginning this week, FWP plans to collect 10 whitefish and 10 rainbow trout from each river. They will be taken to the U.S. Fish and Wildlife Service lab in Bozeman and tested for a parasite that causes kidney disease.

On Aug. 19, FWP closed all recreation on the Yellowstone River and its tributaries from Gardiner to Laurel after staff counted more than 4,000 dead whitefish, along with small numbers of other species. Some parts of the river have been re-opened.