Fishing Henrys Lake

Idaho’s State Fish

Idaho State Parks and Recreation Interpretive Sign: “Henrys Lake has been managed as a trophy fishery since 1976. Cutthroat trout, Idaho’s state fish, are native to Henrys Lake and are found naturally in more Idaho waters than any other trout or salmon. They are easy to identify – just look for the bright red ‘slash’ under their jaw. Steelhead and chinook and sockeye salmon are all ocean-going cousins of the cutthroat. The trout spawn in the spring but begin the journey to tributaries during late fall and early winter. Trout fry stay in the tributaries for a year before heading to the lake where they will live for about six years. Lake-dwelling cutthroat commonly grow to about 20 inches and can weigh as much as 20 pounds! Most of the cutthroat in Henrys Lake weigh three to five pounds.”

Henrys Lake Habitat

Idaho State Parks and Recreation Interpretive Sign: “The lake level fluctuates little and is dependent upon irrigators’ needs and climactic changes, like prolonged drought. This constant elevation provides excellent fish habitat, and Henrys Lake is renowned for its world-class fishing. No local, state or federal money was used to create this reservoir. Instead, the farmers and ranchers who use the reservoir’s water funded the construction of the dam.”

The Last Two Ice Ages

Idaho State Parks and Recreation Interpretive Sign: “How was Henrys Lake Formed? Two ice ages existed in this area. The most recent, known as the Bull Lake Ice Age, occurred approximately 140,000 years ago and lasted about 50,000 years. During this time, glaciers formed on Sawtooth Peak (located behind you and to the left) and on Targhee Peak. When the glaciers melted, the water flooded this valley, forming Henrys Lake. Henrys Lake was probably formed about 9,000 years ago during the last ice age, at about the same time the Great Lakes were created in the northern United States. Those huge lakes were probably formed by moving sheets of ice while Henrys Lake was created by a mountain glacier that dammed the Snake River valley between the Henrys Lake Mountains and the Centennial Range.”

Glacial Formation

Idaho State Parks and Recreation Interpretive Sign: “You are standing on a ridge made up of rocks moved by water which is combined with glacial till, rocks which are broken and carried or pushed by the action of a glacier. This ridge does not support many trees since the glacial material does not retain water as well as other types of soil.”

Finding Fossils and an Ancient Sea

Idaho State Parks and Recreation Interpretive Sign: “Signs of an Ancient Sea: Millions of years ago, before the ice ages, there was a large inland sea covering this area. If you look closely, you may see evidence of the ancient sea floor bottom by finding tiny crinoid fossils embedded in the limestone rocks along the trail.”