Recent Lab Results Show Clearer Picture of Extent of Yellowstone Parasite

Montana Fish, Wildlife and Parks has received results from additional testing performed last week on fish samples collected as part of the effort to better understand the distribution of the parasite in the Yellowstone River and its tributaries.
 
From the upper Yellowstone, tests were performed on 30 trout collected at spring creeks close to the area experiencing the highest level of Whitefish mortality. Two Brown Trout from Nelson’s Spring Creek tested positive for the presence of the parasite, while all other fish (13 Rainbow Trout and 15 Brown Trout) tested negative. It is important to make clear that there was no evidence of disease detected (presence was that of parasitic infection only) at any of these locations and no mortality documented. All the samples tested were healthy and alive when collected.

Tests were also performed on Whitefish samples collected at the mouth of the Boulder River, at Holmgren Ranch Fishing Access Site near Columbus, and at Laurel where 11 Whitefish tested positive. From these same downstream locations, three Rainbow Trout tested positive, one tested negative.
     
All tests on Yellowstone River samples are being performed by the U.S. Fish and Wildlife Service Bozeman Fish Health Center. Results are pending on a number of additional samples collected at the mouth of Big Creek near Emigrant, on the Shields River below the Chadbourne diversion dam, the Jefferson River at Sappington Bridge, as well as the Stillwater River and Boulder River where they meet the Yellowstone.

FWP fish health specialists note that fewer dead fish and less disease have been observed recently, but crews are continuing to perform surveys.

FWP continues to evaluate these results and will keep the public informed as to any decision related to reopening sections of river to recreational uses.
 
Updates on the Yellowstone fish kill can be found on our website here: http://fwp.mt.gov/news/newsReleases/headlines/nr_4278.html.