Sand Island to Mexican Hat
Sand Island, the BLM boat ramp and campground about 3 miles west of Bluff off US-191, is the standard launch for the upper canyon, the float to Mexican Hat past the petroglyph panel at the ramp, the River House ruin and the cut through Comb Ridge. A BLM permit from the Monticello Field Office is required year-round for any float between Montezuma Creek and Clay Hills, with a lottery for launches from April 15 to July 15. The south bank is Navajo Nation and camping there needs a Navajo Nation permit as well.
Mexican Hat to Clay Hills
Below the Mexican Hat ramp on US-163 the river enters the Goosenecks and the lower canyon, a 57 mile Class I-II run (with one Class III rapid) to the Clay Hills take-out on an 11 mile dirt road off UT-276 at the head of Lake Powell. This is a multi-day trip through the deepest part of the canyon, with camps on both banks and no road access in between.
Bluff
Bluff is the base town for the river, with outfitters, shuttles and lodging, and the Sand Island ramp is where most day use happens. Below the town the river is a silty, warm desert stream, and the sediment load is heavy enough that filtering river water on a trip is impractical; boaters carry their own.
Channel catfish and carp
There are no trout in the San Juan in Utah. By the time the river reaches Bluff it is warm, turbid desert water far below the Navajo Dam tailwater in New Mexico, and the fish an angler will actually catch here are non-native channel catfish and common carp. Catfish are abundant enough that the San Juan River Basin Recovery Program removes thousands of them each year between Four Corners and Sand Island to protect native fish. Bait fished on the bottom in eddies and pool tailouts from camp is the standard approach; bass are not a meaningful part of the catch here.
Endangered native fish
The San Juan is critical habitat for Colorado pikeminnow and razorback sucker, both federally endangered, along with native suckers and chubs. Any pikeminnow or razorback caught must be released immediately unharmed, and the recovery program asks anglers not to move any fish between waters. Utah regulations treat this reach as a warmwater fishery; there are no trout limits because there are no trout.
Season and regulations
Flow is the trip planner's number, not the angler's. American Whitewater lists 500 to 8,000 cfs at the Bluff gauge as the runnable range, the BLM recommends at least 500 cfs for loaded rafts, and spring snowmelt from the San Juan Mountains normally provides the best flows from April into June; late summer can drop below the practical minimum. This page compares the Bluff gauge to that float range.
A Utah fishing license is required, and the statewide limits for catfish and carp apply. Endangered pikeminnow and razorback sucker must be released. Float permits are issued by the BLM Monticello Field Office and the Navajo Nation for left-bank camps. Check the current Utah Division of Wildlife Resources fishing guidebook and the BLM San Juan River permit page before you go.