- Location: Garfield County
- Directions: 15 miles south of Panguitch on U.S. 89 then west from the town of Hatch on the Fish Hatchery Road
- Type: Fishing
- Size: 23 miles of stream
- Elevation: 6,900 to 9,680 feet
- Hours: No restrictions
- Likely catch: Brown Trout, Rainbow Trout
- Possible catch: Brook Trout, Cutthroat Trout, Mountain Whitefish
- Regulations: To see what statewide or special regulations apply to this waterbody, please read the current Fishing Guidebook.
- Site amenities: Much of the stream is walk-in access on private land. Gasoline, lodging, and stores are available in the nearby towns of Hatch and Panguitch.
- Handicap access:
- Site description: This is a popular stream but much of it is on private land. Some landowners have traditionally allowed access to fishermen but the area is changing each year with new summer home development along the steam. Fishermen are responsible for obtaining permission to fish on private land and should obey signs and keep out of posted areas. There are a number of distinct areas along this stream that offer different types of fishing. Starting at the lower end of the stream and its confluence with Asay Creek and then working upstream, these areas are as follows:
Public access is possible on some of Mammoth Creek west of Highway 89�please watch for and respect private property postings.
1. Confluence with Asay Creek upstream to Mammoth Creek Fish Hatchery about two miles of stream. Asay Creek and Mammoth Creek converge to form the upper Sevier River. Some of Mammoth Creek in this area is closed to public access. Fishing is mainly for brown trout and some whitefish near the confluence. Brown trout fingerlings are stocked in this area and also in Asay Creek and the upper Sevier River. This area can offer good fishing in late fall, winter, and early spring. Spring runoff and summer rainstorms can turn the stream muddy.
2. Mammoth Creek Fish Hatchery upstream to Canal Diversion about three miles of stream. This area is seasonally de-watered for irrigation use and is only a marginal fishery. Much of this area is posted against public trespass.
3. Canal Diversion upstream to the end of the Hatch Meadow about nine miles of stream. This area offers good fishing for wild brown trout. Browns range in size up to about 19 inches. This stream is all on private land, but much of it is open to public fishing. Respect private lands and keep out of posted areas. Many new houses are being built in the lower end of this area and some of the stream might be closed to trespass. Access in this area is also limited to a gravel road, but it is usually passable in a passenger car.
4. Upper end of Hatch Meadow to Mammoth Spring about three miles of stream. This area consists of the old summer home area. Flows are greatly augmented in this area because of the spring, but water temperatures are very cold even during the summer. Consequently, abundance of wild trout is not great. Some wild brook trout occur in this area. Tommy Creek, a small tributary stream also has a good population of brook trout. The trout population is augmented by stocking of brook trout fingerlings and catchable-size rainbow trout.
5. Mammoth Spring to headwaters and confluence with Louder Creek about six miles of stream. The stream is much smaller above Mammoth Spring. It extends into Iron County and is relatively high elevation. The stream is located on Forest Service lands and open to the public. It can be reached from the road between Panguitch Lake and Cedar Breaks National Monument, but much of it is remote and limited to walk-in access. Besides Louder Creek, Castle Creek is another small tributary in this area. Brook trout and cutthroat trout are abundant in this headwater area.
Other nearby waters include Duck Creek Pond, Aspen Mirror Lake, Navajo Lake, Panguitch Lake. Panguitch Creek, Asay Creek, and the upper Sevier River.