Greenback Cutthroat Trout (Oncorhynchus clarkii stomias) in spawning colors.

Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias).
Rocky Mountain National Park, Colorado.

A hatch of mayflies against the setting sun. Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado.

Late summer clouds pass over Mout Ikoko above Mirror Lake, Rocky Mountain National Park, Colorado.

Brook trout (Salvelinus fontinalis) in the clear, cold autumn waters of Colorado’s Rocky Mountain National Park.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado. By late summer higher than natural levels of nitrogen and other pollutants cause increased algae growth.

A small tributary in a hidden gorge. Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado.

Greenback Cutthroat Trout (Oncorhynchus clarkii stomias). Rocky Mountain National Park, Colorado.

North Inlet Creek, Rocky Mountain National Park, Colorado.

Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus). Rocky Mountain National Park, Colorado.

Ptarmigan Mountain, Rocky Mountain National Park, Colorado.

Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus). Rocky Mountain National Park, Colorado.

Brook trout (Salvelinus fontinalis) Rocky Mountain National Park, Colorado.

Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus). Rocky Mountain National Park, Colorado.