Fishlake is a high alpine lake (elevation approximately 8,848 ft) located in the Fishlake/ Southern Wasatch Plateau region of south-central Utah and is what the Fishlake Mountains are named after. It lies within and is the namesake of the Fishlake National Forest.
The lake, five miles long by one and a half miles wide at its widest point, lies in a geologic structure known as a graben valley. It is bounded by the Mytoge Mountains on the south-east shore which rises sharply to over 1,000 feet above the lake level. Along the north-west shore the lake is bounded by Fish Lake Hightop Plateau (elev. ~11,600 ft). Based on recent research the lake has an average depth in summer of about 100 feet and has been found to be 127 feet deep in its deepest known location.
The lake is best known for its sport fishing—particularly its large lake trout (also known as mackinaw). Fish are caught every summer upwards of 25 lbs. The region sees heavy snowfall in the winter, with snowfall occurring as late as June in any given year. For this reason tourist activity is at its peak in the summer months.
Fly fishing this big lake can be rewarding from a boat as there are plentiful shallow shorelines which are productive with a fly. For the discriminating fly fisher, if you put your time on this lake or hire a guide, it will reward you with some big fish. Monster Brown and Splake (lake trout/brook trout hybrid) can be found in the fall if you look hard. Look for the big Mackinaw in the springtime.
More importantly, the neighboring streams to the lake are Sevenmile Creek and UM Creek which downriver form the headwaters of the Fremont River. Sevenmile produces large quantities of Brook trout in the 6-10 inch range and UM supports a healthy population of re-introduced Colorado River Cutthroat from 6-16 inches. Tiger Trout can be found as well and some may reach or exceed 20 inches, but they are very wiley and hard fighting bruisers.
If you put in some time scouting out the area, you will find beavers in full force on this mountain. There are many beaver ponds worth fishing and none of which will produce a monster brook trout. They are fun to fish and a good trade-off to the summer heat and other anglers down the mountain.
Johnson Valley reservoir is formed about 8 miles from Fishlake by Sevenmile Creek and various springs. Then UM Creek and the Fremont River converge into Mill Meadow Reservoir. This stillwater holds much of the water which feeds the middle section of the Fremont River and eventually the lower river. Mill Meadow is home to Rainbows and nice Tiger Trout.
The upper Fremont River between Johnson Valley Reservoir and Mill Meadow Reservoir has some quality water, but due to the farmers using this water for irrigation, the summer months bring higher water and less fishability. Spring and fall are a better bet for the fly fisher as water is low and clear and perfect for dries or nymphing. Perhaps the best indicator of good fishing here is due to the season. As with most lakes, there are times when an angler can find bigger fish or more opportunities for success due to temperatures in the lake, fishing pressure and fish habits.