In September, Colorado Parks and Wildlife (CPW) stocked 480 Trojan male or YY brook trout into Bobtail and Steelman creeks in an effort to restore native cutthroat populations in the headwaters of the Williams Fork River.
In 2010, an alarming number of non-native brook trout were discovered after completing a fish survey in the headwaters of the Williams Fork River.
While it is unknown when brook trout invaded these creeks, it was evident the thriving brook trout had nearly decimated the native cutthroat population over time.
Cutthroat trout found within these two creeks are some of the highest-valued native cutthroat populations in the headwaters of the Colorado River basin.
Considered a species of special concern in Colorado, this subspecies of trout is genetically pure and naturally reproducing.
“In 2011 we found 123 cutthroat trout combined in both creeks. Today, after 13 years of hard work by dedicated biologists we are seeing a little more than 1,400 cutthroats in these creeks,” said CPW Aquatic Biologist Jon Ewert.
Trojan male brook trout are often called YY because they have two Y chromosomes, unlike wild males with an X and Y chromosome. These trout are stocked into wild brook trout populations and reproduce with the wild fish, producing only male offspring.
Without females to complete a reproducing population, biologists hope the brook trout will eventually die out, allowing for native cutthroat trout to be restored.
Colorado Parks and Wildlife plans to stock both streams with YY brook trout over the next several years to sustain the number of Trojan males in the population, eliminating the production of female brook trout in the creeks.
source: Colorado Parks and Wildlife