Curious Nature: Native beauties in our waterways
Vail, CO Colorado
As the snow quickly recedes in our valley and the bodies of water begin to rise under the heat of the spring sun, people will be out attempting to extract some of the underwater residents of our streams, rivers and ponds. While the die-hards have been out all winter in this mild winter we’ve experienced wetting their lines, the less dedicated will soon be out joining them. Few of those river, stream and lake residents are native to this area. Without past introduction of other species, seekers today would only be able to experience one type of trout in our waterways: the cutthroat trout.
Four different cutthroat species evolved right here in Colorado, with three of them still in existence today, although differentiating them by sight is virtually impossible. Subspecies identification has been done through genetic testing, and each subspecies is unique. The different subspecies are grouped by their native range: The Rio Grande cutthroat found in the San Juans, the Greenback found in the South Platte and Arkansas River drainage and the now extinct yellowfin cutthroat. The yellowfin cutthroat called the Twin Lakes of the Arkansas River headwaters home. This brightly colored fish was said to regularly grow for more than 10 pounds, was first identified in 1891 and last spotted in 1903. Today on the Western Slope, the cutthroat subspecies you’re most likely to encounter is the Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus). These trout can be identified by heavier spotting toward their tails and red coloration behind their gills, or near their “throats,” that give the appearance of blood, as if their throats have been cut. This coloration becomes even more vibrant during breeding, usually in June.
With the cutthroat species being our only native species, other species you might encounter in our rivers and streams are the rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta) or the brook trout (Salvelinus fontinalis).
The interaction of the different species is what many scientists are closely watching. Here in Colorado, there has been a large emphasis on maintaining “pure” cutthroat populations. What has become apparent is that rainbow trout have taken over much of the original range of the cutthroat and have bred with the native species, producing mixed-species hybrids of the two. Brown and brook trout are able to out-compete cutthroat for their habitat. Some research states current populations of Colorado River cutthroat trout represent no more than 1 percent of historic populations.
Response to this research, along with more monitoring and protection of the pure population, is helpful to maintaining the biodiversity that our ecosystem naturally has. The Division of Wildlife currently lists the Colorado River cutthroat trout on its threatened and endangered list. Even with this designation, state fishing regulations allow a four-fish bag limit per day on all trout species and an eight-fish possession limit of all trout species.
If you’re lucky enough to see one of these lovely species, take a second and think about the history behind their existence in the incredible rivers, streams and lakes that occupy our state and appreciate the biodiversity we’re lucky enough to observe.
Travis Long is a graduate fellowship educator at Walking Mountains Science Center. As spring arrives, you can find him wandering the streams and rivers of the area, attempting to perfect his fly-fishing cast and exploring all parts of the riparian ecosystem.