- Rating: Slow
- Conditions: Due to an increasing population of illegally introduced smallmouth bass — which posed a serious threat to native fish in the Virgin and Santa Clara rivers — Gunlock Reservoir was treated with rotenone in October 2015. Largemouth bass, bluegill and crappie will be restocked in 2016, but fishing opportunities will be limited for a couple of years while these populations establish.
- Location: Washington County, Northwest of St. George
- Directions: 17 miles northwest of St. George on Highway 18, or 15 miles south of the town of Enterprise
- Type: Fishing
- Size: 268 acres at full pool
- Elevation: 3,550 ft
- Hours: No restrictions
- Likely catch: Bluegill, Green Sunfish, Largemouth Bass
- Possible catch:
- Regulations: To see what statewide or special regulations apply to this waterbody, please read the current Fishing Guidebook.
- Site amenities: A State Park boat ramp and parking lot, primitive camping around the reservoir shoreline, and gas and convenience stores in the nearby town of Veyo, and other facilities available in St. George
- Handicap access:
- Site description: 2005 and 2006 floods added a lot of sediment to the reservoir and plugged the dam outlet works. In 2008, the reservoir was drained to install a new outlet, which would prevent similar problems in the future. Draining the reservoir, however, meant losing the fish populations. Largemouth bass and bluegill were reintroduced in spring 2009, but it will take a few years for these fish to fully establish new populations. There are a lot of small, 6- to 8-inch bass present in 2010, though these fish will grow fast. By 2011, 10- to 12-inch fish should be abundant. The native-fish management plans for the Santa Clara River do not allow for catfish to be stocked in the drainage, so Gunlock's limited catfish population will not be reestablished.
Gunlock reservoir was completed in 1970. The original reservoir plan included the 3,300 acre-feet fishery conservation pool. The reservoir was initially stocked with largemouth bass, bluegill, and black crappie.
The conservation pool agreement with the local irrigation company was amended in 1982 to clarify dead storage water, which cannot be drained from the reservoir, and active storage water. Provisions were also made to stabilize spring water levels to benefit bass spawning and hopefully curb a declining bass population.
The agreement was amended again in 2001 with a new agreement with the Washington County Water Conservancy District. The new agreement reduced the conservation pool to a level of about 2,325 acre-feet. The agreement also reestablished minimum in-stream flows downstream from Gunlock Reservoir, in the Santa Clara River, to help native fish avoid being listed under the Endangered Species Act. In turn, a conservation pool was acquired in the new Sand Hollow Reservoir. Even after the size reduction, Gunlock Reservoir is one of the largest conservation pools in southern Utah.
The efforts to stabilize water levels during spawning seasons probably helped the bass population, but overall numbers did not respond as hoped. Restrictive fishing rules, that required catch and release of most sizes of bass, were introduced in the early 1990s. These rules were patterned after similar rules at Quail Creek Reservoir and remain in effect today. The bass population has improved as a result of these measures.
Gunlock Reservoir has a reputation of producing big, difficult-to-catch bass. Although Quail Creek Reservoir and Sand Hollow Reservoir are better known for bass fishing, some local anglers prefer Gunlock Reservoir and would like to keep it out of the spotlight.
The water temperatures stay cooler longer at Gunlock Reservoir, into the spring and summer, because of the slightly higher elevation than the other major Washington County reservoirs. Good spring fishing for bass and bluegill is often delayed into May with a peak in early June, which disappoints anglers looking for a hotspot in March and April.
Much of the reservoir shoreline is accessible to bank fishing, although a boat makes bass fishing much more effective. Other nearby waters include Baker Reservoir, the Enterprise reservoirs, the Sand Cove reservoirs, Quail Creek Reservoir, and Sand Hollow Reservoir.
A fish consumption advisory has been issued for largemouth bass from Gunlock due to elevated levels of mercury. For details, visit www.fishadvisories.utah.gov.