Yellowfin cutthroat trout

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iCutthroat trout
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Salmoniformes Family: Salmonidae Genus: Oncorhynchus Species: O. clarki
Trinomial name
Oncorhynchus clarki macdonaldi Jordan & Fisher, 1891

The yellowfin cutthroat trout ( Oncorhynchus clarki macdonaldi ), a subspecies of Cutthroat trout, was officially identified in 1891 and named after the US Fish Commissioner, MacDonald.

At the end of the last ice-age boulders and clay moraine blocked off a tributary of the headwaters of the Arkansas River in what is now the state of Colorado. The two lakes which formed were named the "Twin Lakes" by the area's settlers. Both lakes held small greenback cutthroat trout from the early days of the Wild West, but in the mid-1880s reports circulated of much larger trout, up to 10lb 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 what they proclaimed to be a new species the "yellowfin cutthroat". In his report Jordan took credit for the name and 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'.

Jordan's specimens have recently been re-examined by American biologist Robert 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'.

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 but the yellowfin disappeared completely.