The yellowfin cutthroat trout (''Oncorhynchus clarkii macdonaldi'') is an extinct subspecies or variety of the cutthroat trout, a North American freshwater fish.

Natural history

At the end of the last ice-age boulders and clay moraine blocked off a tributary of the headwaters of the

Arkansas River The Arkansas River is a major tributary of the Mississippi River. It generally flows to the east and southeast as it traverses the U.S. states of Colorado, Kansas, Oklahoma, and Arkansas. The river's source basin lies in the western United Stat ...

in what is now the state of

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

. The two

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

s which formed were named the " Twin Lakes" by the area's settlers. Both lakes held small

greenback cutthroat trout The greenback cutthroat trout (''Oncorhynchus clarkii stomias'') is the easternmost subspecies of cutthroat trout. The greenback cutthroat, once widespread in the Arkansas and South Platte River drainages of Eastern Colorado and Southeast Wyomin ...

from the early days of the Wild West, but in the mid-1880s reports circulated of much larger trout, up to in weight, with bright yellow fins. Recent research has speculated that the yellowfin cutthroat may have been native to the entire Arkansas River basin, not just Twin Lakes.

Discovery and naming

In July 1889, Professor David Starr Jordan and G. R. Fisher visited Twin Lakes and published their discoveries in the 1891 Bulletin of the

United States Fish Commission The United States Fish Commission, formally known as the United States Commission of Fish and Fisheries, was an agency of the United States government created in 1871 to investigate, promote, and preserve the fisheries of the United States. In 1 ...

. They found both the greenback and what they proclaimed to be a new species the "yellowfin cutthroat". In the species description, published in the 1890 edition of the Proceedings of the United States National Museum, Jordan and Evermann described the fish as follows:

''Color, silvery olive; a broad lemon yellow shade along the sides, lower fins bright golden yellow in life, no red anywhere except the deep red dash on each side of the throat.''

The subspecies was scientifically named ''macdonaldi'' after the US Fish Commissioner, Marshall McDonald. Jordan's specimens were re-examined by the fisheries biologist Robert J. Behnke, who commented, "I have no doubt that Jordan was correct; the yellowfin trout and the greenback trout from Twin Lakes were two distinct groups of cutthroat trout".

Extinction

Until about 1903, greenback and yellowfin cutthroats survived together in Twin Lakes, the populations remaining isolated as both breeders and feeders. The end for the yellowfin cutthroat came soon after the introduction of the rainbow trout to Twin Lakes. The greenback population interbred with the rainbows, resulting in

cutbow A cutbow ('' Oncorhynchus clarkii'' × ''mykiss'') is an interspecific fertile hybrid between a rainbow trout (''Oncorhynchus mykiss'') and a cutthroat trout (''O. clarkii''). Cutbow hybrids may occur naturally where the native ranges of both sp ...

s, but the yellowfin disappeared completely. The yellowfin is now extinct.

Natural history

Discovery and naming

Extinction

References

Further reading