Surveys in 2020 showed that tiger trout, a sterile hybrid between a brook trout and a brown trout, are doing well in Cow Lake in the Shoshone National Forest. High numbers of tiger trout between 13.5 and 15.5 inches were captured. The largest tiger trout captured during 2020 Cow Lake sampling was 18.2 inches and 2 lb.
In addition to being a species highly desired by anglers, tiger trout are a good management tool for biologists to control other fish populations. Tiger trout are aggressive predators with a large gape size, which enables them to eat bigger fish than brown trout and brook trout of the same size. The fact that they are sterile ensures that they will not spread to other waters uncontrollably. Tiger trout were stocked in Cow Lake in 2015 and 2019 to take advantage of an abundant lake chub population and create a new sport fishery for Lander-area anglers.
Angler reports also indicate that Upper Silas Lake tiger trout are also doing well. Tiger trout were stocked in Upper Silas Lake in 2014, 2016, and 2018 to improve a stunted brook trout population. The goal of stocking tiger trout in Upper Silas Lake is to reduce the number and thereby increase the size of brook trout as well as create a tiger trout fishery.
Cow Lake is less than a ¼-mile hike east of the Loop Road between Fiddlers Lake and the Little Popo Agie River. An approximate waypoint for Cow Lake is Z 12, E 0674851, N 4720427 (datum NAD 1983). Upper Silas Lake is an approximately four-mile hike from the Christina Lake trailhead (located at Fiddlers Lake) by taking the Christina Lake Trail to the Silas Lake Trail.