der. 
On August 19, 2016 the Montana Department of Fish, Wildlife and Parks Department indefinitely closed the river and its tributaries from the Montana border at Gardiner, Montana to Laurel, Montana to all recreational activity. The 183-mile (295 km) closure resulted from a massive fish kill attributed to proliferative kidney disease, a rare but serious salmonid disease. The parasite-- Tetracapsuloides bryosalmonae—is not harmful to humans or other mammals.  Wildlife officials estimate tens of thousands of fish may have died, mostly mountain whitefish, but Yellowstone cutthroat and rainbow trout have been affected.  The closure is expected to cause significant adverse economic impact to businesses which depend on summer tourist and recreational activities along the river. 
On September 1, 2016 the agency reopened two stretches of the river. The first stretch, from the northern boundary of Yellowstone National Park to Carbella, Montana, was open to non-fishing recreation only to allow the fish population to recover. The second stretch, from Carbella, Montana to Laurel, Montana, was opened to all uses. 
Peak Yellowstone River temperatures exceeded 68 °F (20 °C) for 18 straight days from July 17 to August 4.  Montana Fish Wildlife and Parks notes that trout and whitefish prefer water temperatures close to 55 °F (13 °C). 
The Yellowstone River is considered to be one of the greatest trout streams of the world  and is officially classed as a blue ribbon stream in Montana from the park to the confluence with the Boulder River east of Livingston and from the mouth of Rosebud creek near Rosebud, Montana to the North Dakota border.  The lack of dams along the river provides for excellent trout habitat from high inside Yellowstone Park, downstream through Gardiner, the Paradise Valley, Livingston, and to Big Timber, a stretch of nearly 200 miles (320 km). The Yellowstone varies in width from 74 feet (23 m) to 300 feet (91 m), so fishing is normally done by boat. The most productive stretch of water is through Paradise Valley in Montana, especially near Livingston which produces brown trout, rainbow trout and native Yellowstone cutthroat trout as well as Rocky Mountain whitefish. From Billings downstream to the North Dakota border, anglers seek burbot, channel catfish, paddlefish, sauger, smallmouth bass, and walleye.   The pallid sturgeon (Scaphirhynchus albus), an endangered species endemic to the waters of the Missouri and lower Mississippi River basins, is also found in the Yellowstone.
|Yellowstone Lake to Yellowstone Falls|
Yellowstone River, Fishing Bridge, July 1959
|The river inside Yellowstone National Park provides accessible flat water fishing and abundant Yellowstone cutthroat trout. The portion of the river through the Hayden Valley is closed all year long, but the rest is accessible and easily wadable. No floating is allowed. Numerous insect hatches occur following the opening of the river on July 15 providing anglers the opportunity to try numerous artificial flies including Pale Morning Duns, Green Drakes, Gray Drakes, Caddis and salmonflies.|
|Grand Canyon of the Yellowstone and Black Canyon of the Yellowstone|
Black Canyon of the Yellowstone near Gardiner, Montana
|The canyon reaches inside Yellowstone National Park are accessible only by hiking or horseback. The river here is usually quite swift, with sheer canyon walls in spots. Below Knowles Falls, about four miles upstream from Gardiner, anglers will find browns and whitefish in addition to the rainbows and cutthroat trout.|
|Gardiner to Yankee Jim Canyon|
Just south of Yankee Jim Canyon
|This section of the Yellowstone holds a good population of medium-sized rainbow and cutthroat trout, with a few big browns as well. The first half of this section from Gardiner to the bridge at Corwin Springs is mostly fast water, with some class II and III white water. From Corwin Springs to Yankee Jim Canyon, the river flattens out substantially and gives the angler more time to cast to fish along the banks.|
|Yankee Jim Canyon|
Upper Yankee Jim Canyon
|Yankee Jim Canyon