| Greenback cutthroat trout | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Salmoniformes |
| Family: | Salmonidae |
| Genus: | Oncorhynchus |
| Species: | O. clarki |
| Subspecies: | O. c. stomias |
| Trinomial name | |
| Oncorhynchus clarki stomias (Cope, 1871) |
|
The greenback cutthroat trout (Oncorhynchus clarki stomias) is the easternmost subspecies of cutthroat trout. This subspecies, once widespread, today occupies less than 1% of its historical range and is currently listed as threatened under the Endangered Species Act. It was adopted in 1994 as the state fish of Colorado.
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The greenback cutthroat's maximum size is 18 inches (46 cm). It has the largest spots of all cutthroats and is reported to have the most brilliant spawning coloration. Like all cutthroats, it has red coloration in the area of the lower jaw and throat. Historically, it has been reported to grow as large as 4.5 kilograms (9.9 lb).
The cutthroat trout is thought to have evolved over the past two million years from other Oncorhynchus species which migrated up the Columbia and Snake river basins to the Green and Yellowstone river basins. Within the past 20,000 years, a population which crossed the Continental Divide during the most recent Ice Age gave rise to the greenback cutthroat.
The greenback cutthroat trout today is found east of the Continental Divide in the cold, clear foothill and mountain waters of the Arkansas and South Platte Rivers. Although it was common in the late 19th century, ranging along the Front Range from Wyoming to New Mexico, it began to decline when settlers arrived in the area. Mining in its native river basins led to sediment and toxic runoff in the water. These factors, along with water diversion for agriculture and overfishing, led to the decline of many greenback cutthroat trout populations.
The introduction of non-native species such as brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (O. mykiss) was also detrimental to the greenback cutthroat. The former two species competed with greenback cutthroats while the latter hybridized with it, creating cutbows. Other subspecies of cutthroat were introduced to greenback habitat, further damaging populations due to hybridization.
Although the greenback cutthroat was considered extinct by the 1930s, in 1957 a population was discovered in Rocky Mountain National Park in the Big Thompson River, a tributary of the South Platte. Additional populations were found in 1965 and 1970, making possible the listing of the subspecies as endangered under the 1973 Endangered Species Act. Recovery efforts for the greenback cutthroat by the U.S. Fish and Wildlife Service, assisted by Trout Unlimited, are ongoing and seemed to have made it possible to upgrade its status to threatened. However, it was recently determined that due to insufficient study of the original stock most if not all animals in the reintroduction program were actually the similar Colorado River cutthroat trout.
Catch and release fishing of the greenback cutthroat is currently permitted in parts of both the South Platte and Arkansas River basins.