The Yellowfin Trout

The story of the yellowfin cutthroat, initially named Salmo mykiss macdonaldi in 1891 after the US Fish Commissioner MacDonald, (now Salmo clarki macdonaldi) is one of the most mysterious of all wild trout stories. The variety appeared as if from nowhere; and has now disappeared without trace.

At the retreat of the last glaciation, boulder clay morraine blocked off a tributary of the headwaters of the Arkansas River in what is now the state of Colorado. Two lakes were formed, which the early settlers named Twin Lakes. They were known to hold small greenback cutthroat from the early days of the Wild West, but in the mid-1880s there were reports of much larger trout, up to 10Ib in weight, with bright yellow fins.

In July 1889, Professor D. S. Jordan and G. R. Fisher visited Twin Lakes, and published their discoveries in the 1891 Bulletin of the US Fish Commission. They found both the greenback and the new yellowfin cutthroat. In his report Jordan named the latter and described it 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'.

Jordan's specimens were recently re-examined by the American biologists Robert Behnke, who concluded that, '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.'

Through to about 1903, greenback and yellowfin cutthroats survived together in Twin Lakes, remaining isolated as both breeders and feeders. Then the introduced rainbow trout took a firm hold; the greenback population was ruined by hybridization and the yellowfin completely disappeared. The introduction of a foreign trout had resulted in the loss of a special form of wild trout: for ever.