GRAND CANYON NATIONAL PARK
Historically, only 8 species of fish lived in the Grand Canyon portion of the Colorado River. All of them were classified as either minnows or suckers. Only 5 of the 8 still exist, and most of them have been relegated to tributary waters for survival. Decreased flow due to the Glen Canyon Dam slowed the waters, raised the temperature, and otherwise affected the habitat.
Rainbow trout and brown trout are primary invaders that have taken advantage of the new system. A fishery program regulates sport harvest of every fish through the Grand Canyon and is working to help restore a more natural order. Unfortunately, things will never return to their endemic state.
YELLOWSTONE NATIONAL PARK
Two species of this red-slash throated fish navigate the waters in the park: the Yellowstone Cutthroat and the Westslope Cutthroat. The Yellowstone Cutthroat provided a primary food source for birds, mammals, and even humans for thousands of years. Population numbers dove steeply in the 1980s and only 538 breeding fish were counted in 2004. The introduction of Lake Trout has been battled in Yellowstone, and numbers are back on the rise. A 2013 net study showed numbers at almost 2/3 of their historical levels. Management plans are bringing back this outstanding fish.
Historically a stream dwelling fish, the Arctic Grayling has been all but removed from Yellowstone due to invasive species. A couple of lake populations remain inside the park boundaries, but moving water populations are absent. Yellowstone fisheries managers are actively working to restore the Arctic Grayling to some of his original habitat inside the park.
The Mountain Whitefish is a hardy species that has bucked the trend of being driven out by invasive species. Anglers today frequently catch them in Yellowstone larger rivers while targeting trout. They prefer the deep, clear pools of water and are extremely sensitive to pollution.
This bottom dwelling fish prefers cold, shallow water. It feeds on most anything that will fit in its mouth, but does not grow much over a few inches long. Primarily, this fish provides a food source for the larger game fish in Yellowstone.
Several species make up this illustrious group. The largest of them is the Utah Chub, growing up to 12 inches in length. Longnose and Speckled Dace, and Redside Shiner round out the Yellowstone minnows. Each of them can be found in a number of waterways, especially the Snake River drainage.
BRYCE CANYON NATIONAL PARK
The headwaters of many small creeks originate in Bryce Canyon National Park. Rainbow and Brown trout enjoy the habitat of these pristine streams. The surrounding region is known for some of the best fly fishing in the United States.
ZION NATIONAL PARK
The Virgin River system within Zion National Park proudly hosts all 4 of its original native species: Virgin River Spinedace, Speckled Dace, Flannelmouth Sucker, and Desert Sucker. All of them have adapted to the difficult living conditions presented by their environment. Rapid temperature changes and heavy silt distribution are but two of the difficulties presented to these fish.
Invasive species have shown up in the system. Brook, Brown, Cutthroat, and Rainbow Trout are all found in the system now, but not yet in heavy numbers. Another invader to the region is the Channel Catfish. Efforts are underway to keep these recent party crashers from disrupting the entire ecosystem, lent to have done in the Colorado River.