The Grey Reef section of the North Platte River originates in Central Wyoming near Alcova, about 25 miles southwest of Casper. Grey Reef is a four-hour drive from Denver and 5-1/2 hours from Salt Lake City. Casper is served by flights from major airlines in Denver and Salt Lake City.
Although the most popular sections of Grey Reef comprise the upper 13 miles, there are actually 83 miles of highly productive trout water in the Grey Reef System. The upper 13 miles maintain good water quality through the brief spring runoff; the entire stretch fishes well during the rest of the year. Grey Reef produces year-round, as it is ultra insulated from runoff by 5 reservoirs tightly spaced upstream. Grey Reef Dam was completed in 1961 and has preformed its duty as an after bay to Alcova Reservoir ever since. The North Platte River below Alcova Dam was subject to wild changes in daily flow due to electricity demands prior to Grey Reef Dam. Now, the flows are consistent and only increase or decrease with seasonal demand. The river intersects classic western sagebrush prairie and is flanked by a variety of landscapes including rolling hills, mountains and cottonwood bottoms.
The trout populations average 3,000 fish per mile with 90% being rainbow and 10% browns and Snake River cutthroat. Grey Reef is notorious for the large average size of its trout and the massive size of its trophy class trout. The average rainbow is 16 to 17 inches while a trophy is generally regarded as starting at 25-inches and upward of the low 30-inch range. These fish can weigh from 6- to 15-pounds and more.
Nymphing is the primary mode of fishing during all seasons and water levels. A long leader of 9- to 12- feet and heavy weight can be used with great success, but a short 3- to 6-foot leader with light weight will target trout actively feeding on emergers. 3- to 5x tippets are appropriate for nymphing depending on the hatch, flies and water conditions. Streamers can be tethered to a sink tip line with a 4-foot leader or a floating line with 7- to 9-feet of leader. Dry flies are best presented with 4- or 6x tippet and a leader of at least 8-feet.
The trout at Grey Reef are generally oriented toward the deeper troughs in the middle of the river as Grey Reef has little edge structure, especially at lower flows. Greater success is typically found by placing your boat closer to the bank and fishing out toward the runs, troughs and tail-outs rather than fishing along the banks. The same is true for wading. The exception would be in high water conditions where the depth becomes conducive for trout to forage and seek refuge along the banks. Aquatic life in Grey Reef is abundant and scuds, midges, leeches, worms and crawfish are always available to the trout. Spring is generally regarded as primetime, but Grey Reef fishes well all year. Spring features a healthy baetis hatch, which present great emerger style nymphing, some dry fly opportunities and even some effective streamer options. As the baetis hatch wanes in mid- to late-May, the pale morning duns, caddis and little yellow sallies make their appearance. Nymphing remains king during these hatches, but dry fly fishing, while isolated, can be excellent. Tricos will make their presence in mid- to late-July and this is by far Grey Reef’s most productive and predictable dry fly opportunity.
Tricos will be a force nearly every morning until mid- to late-Sept. Caddis are an important source of food throughout the summer and fall with nymphing primarily in the afternoon and switching to dry fly near dusk. Streamer fishing also gains steam during the summer as fry and crawfish become more available for trout forage. Hopper fishing can be excellent in late-July to mid-Sept., but this is not a predictable phenomenon. September welcomes temperate weather conditions and the forgotten pseudo hatch. The pseudo are normally an early afternoon hatch and the trout will snug themselves into shallow tight riffles to snack on the emergers. However, the trout will soon orient themselves to take the duns off of the surface until early evening. Late-September to early-October will usher in the fall baetis hatch where light nymph rigs and dry fly are effective. Fall is streamer time on Grey Reef. Targeting a trophy trout with a sink tip and a short leader or a floating line and a longer leader can be heart pounding. After the fall baetis have disappeared, prolific midge hatches will offer nymphing and dry fly throughout the winter while solid streamer fishing remains. Nymphing leeches, scuds, worms and midges will be a staple until the next year’s spring baetis arrive.
The Grey Reef section emerges from the Grey Reef Reservoir’s dam. Grey Reef Reservoir is a small impoundment or afterbay a short distance downstream of the much larger Alcova Reservoir. The afterbay’s job is to regulate the flow of water downstream and it also happened to create a world class fly fishing destination.
Grey Reef fishing is easily accessed by drift boats and is an easy river to navigate. There are drift boat rentals available for the angler who doesn’t own or want to haul their own boat to Grey Reef. A river shuttle service is available through The Reef Fly Shop. We will safely transfer your vehicle and trailer from the ‘put in’ to the ‘take out’. Grey Reef fishing is a very forgiving place to wade since the river bottom is not difficult to walk on. The bottom of the river is a variety of sand, gravel, cobble, and silt.
While Grey Reef has plenty of public access, most of it flows through private land. In Wyoming, the bottom of the river belongs to the land owner, as is the case in Colorado. In some states, like Montana, the land between the ordinary high water mark is public domain; this is not so in Wyoming. Wading, anchoring, or even beaching your boat is considered trespassing in Wyoming. But, this fact keeps pressure low on most of Wyoming’s rivers and the fly fishing productivity high.
The North Platte River originates in Northern Colorado just across the continental divide from major tributaries of the Colorado River system. It relies on snowpack from the mountains of the Routt National Forest in Northern Colorado and the Snowy and Sierra Madre Ranges in the Medicine Bow National Forest of Southern Wyoming. The river flows north out of Colorado to Casper, where it turns to the east and joins the Missouri River in Nebraska. Grey Reef is historically not a trout environment, but the construction of several dams, and most importantly, Grey Reef Dam gave rise to a spectacular cold water fishery.
The lower North Platte River was stocked with trout in the 1890s and Grey Reef was first stocked the spring following the completion of the dam. The lower sections are still stocked today. The upper 8 miles from Grey Reef Dam to the Lusby Access are a “trophy fishery” where natural reproduction is the singular source of trout recruitment. The Wyoming Game and Fish Department along with the US Bureau of Reclamation have instituted a flushing flow program for Grey Reef. For 5 days each spring (and sometimes in the fall) the flows from the dam are dramatically increased and systematically decreased to purge the spawning gravel of silt that might otherwise inhibit survival of trout eggs. Since 1996, the flushing flow program has helped create a venue for excellent natural reproduction on the entirety of Grey Reef.
Visit Grey Reef with the expectation of nymph fishing for the highest productivity and be pleasantly surprised when dry fly and streamer opportunities present themselves. Fishing pressure is comparatively low and at times you may not see another boat during your day. There are several campgrounds and lodging facilities in the vicinity although dining options are limited. It is close to Casper, Wyoming’s second largest city that has all the services you may need. Grey Reef is easily accessible, it is easy to navigate and it is a consistent and reliable fishery with a strong potential to produce the trophy trout of a lifetime.