- Rating: Slow
- Conditions: Although the reservoir is almost full now, it was mostly drained last summer due a malfunction in the outlet. It is unclear how many fish were lost. Access is difficult because of deep snow and drifts. Call the Quiet Fly Fisher fly shop at (435) 616–2319 for up to date conditions and fishing reports.
- Location: Sevier County, north of Loa
- Directions: Drive 47 miles southeast of Richfield on SR-24, turn north at Loa and drive on SR-72 for 8 miles
- Type: Fishing
- Size: 171 acres
- Elevation: 7,989 feet
- Hours: No restrictions
- Likely catch: Splake, Tiger Trout
- Possible catch: Cutthroat Trout
- Regulations: To see what statewide or special regulations apply to this waterbody, please read the current Fishing Guidebook.
- Site amenities: A paved boat ramp, and primitive camping on Forest Service lands
- Handicap access:
- Site description: Forsyth Reservoir inundates lower UM Creek. The outflow stream flows through a short canyon accessible only by hiking and then enters Mill Meadow Reservoir. Forsyth Reservoir has a reputation for being an excellent trout producer. Although there is no conservation pool and the reservoir is occasionally drained, the water users usually try to maintain the sport fishery. After complete draining, the fishery recovers surprisingly fast. Even without stocking, considerable numbers of trout re-enter the reservoir from upstream.
The reservoir was treated with rotenone in 1959 to remove problem nongame fish, and again in 1992 to protect downstream fish hatcheries from whirling disease. Following the 1992 treatment, the reservoir was re-stocked with wipers, a white bass and striped bass hybrid. Yellow perch were also stocked as a secondary sport fish and as forage fish for the wipers. This was done on an experimental basis and to allow time for downstream fish hatcheries to take corrective measures to prevent potential contamination from diseased trout.
By 1995, the Utah Division of Wildlife Resources decided that a trout fishery should be re-established. The remaining yellow perch and wipers were removed by another rotenone treatment. Brook and rainbow trout were also removed from UM Creek upstream from Forsyth Reservoir, initially because of whirling disease. Instead of re-stocking rainbow and brook trout, however, sterile hybrid trout were reintroduced. Secondarily, this became an opportunity to re-establish native Colorado River cutthroat trout.
The sterile fish stocked into Forsyth Reservoir are not as susceptible to whirling disease and also help protect native cutthroats from hybridization. Hybrid tiger trout, brown trout crossed with brook trout, and hybrid splake, lake trout crossed with brook trout, have done well in the reservoir. Overall, about 9,000 of each fish are stocked annually, which helps keep this sport fishery popular.
Nearby fisheries include small lakes on the Thousand Lake Mountain, Mill Meadow Reservoir, Johnson Reservoir, Fish Lake, UM Creek, Sevenmile Creek and the Fremont River.