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The Trojan YY brook trout could help restore native fish in Northern New Mexico

"Every collectivist revolution rides in on a Trojan horse of EMERGENCY."

Herbert Hoover

brook trout spots

Last fall, a Lake City, Colorado man caught a new Colorado state record brook trout in Waterdog Lake. The fish was an impressive 26.25" long and measured 16" at the girth. An amazing catch by any standards. The thing is, brook trout don't belong in Colorado. Or the west at all.

Brook trout (Salvelinus Fontinalis) are not actually members of the trout family. Brook trout belong to the char family which includes fish like the Arctic char, Lake trout and Bull trout. Brook trout are the only native "trout" species to the east coast and should be found in the cold water streams of the Appalachian Mountains, from Georgia to Canada. These dynamically colorful fish were a staple in the indigenous people's diets and were considered a gift from the Spirit Leaders. When the Europeans arrived, so began the decline of the brook trout and their habitat. Widespread timber harvesting quickly eliminated shade from the streams. Removing shade and trees takes away vital habitat for insects that the fish feed on, allows the water to heat up and increases siltation. Practices like "log driving," where winter felled timbers are slid into the river over the snow and left until spring, relying on the springtime run-off to wash the logs down stream to a processing station, also destroyed habitat along the fragile riparian borders.

Brook trout were further displaced by the introduction of non-native salmonids such as rainbow trout and brown trout due to their ability to tolerate the warmer water temperatures. After over 100 years of steady decline in their native range, brook trout restoration projects are now underway to once again populate streams with their native inhabitants; in the forests where the brook trout had been nearly extirpated in the east.


brook trout

"Ah how shameless -- the way these mortals blame the gods. From us alone, they say, come all their miseries, yes, but they themselves, with their own reckless ways, compound their pains beyond their proper share.”

The Odyssey

For now, anglers wanting to catch brook trout, it seems like the mountain west is the place to find them. Brook trout were introduced in the west in the mid 19th century. Northern New Mexico has a strong population of brook trout today, superseding and threatening the native cutthroat populations in some high elevation creeks. These populations are now being targeted by the New Mexico Department of Game and Fish, with help and research from New Mexico State University, for eradication by a new management strategy pioneered by the Idaho Department of Fish and Game. Liberal fishing restrictions implemented by states like New Mexico, Colorado and Wyoming haven't proven to be enough. Rather than expand additional catch and keep manual fishing technics or by using potentially harmful piscicides, several western states have opted to deploy the Trojan male.

Rio Grande Cutthroat trout

There are 14 subspecies of cutthroat (Oncorhynchus clarkii) trout in the US. Each has evolved to survive in their their own specific rugged niche habitat. New Mexico is home to one; the Rio Grande cutthroat (Oncorhynchus clarkii virginalis). Because the Rio Grande cutthroat trout holds such a high conservation value in New Mexico, the push to restore them to their native habitat is strong.

The plan is simple.

(just kidding)

Here is where you will wish you had payed better attention during your high school genetics class. A feminized male brook trout, the "Trojan," is introduced into populations of brook trout that are targeted for eradication. Males naturally have both X and Y chromosomes. Females only have the X chromosome. When fish breed, the male fertilizes the egg and passes on either the X or the Y, determining the sex of the new baby fish. But by exposing male brook trout to female hormones in a lab, male trout will actually begin to produce eggs. (whoa!) Those eggs contain both the X and Y chromosomes.

(Stay with me here!)

Those eggs are then fertilized by a normal X/Y male fish and 1/4 of the offspring will be YY chromosome carriers. Those YY males are then stocked into a population of non-native brook trout eventually turning the entire populations into only male fish. An all male population, without females to breed with, becomes self limiting. These Trojan fish look and act like a brook trout that has not been tampered with genetically. Brook trout can reproduce at age 1. By contrast, cutthroats begin spawning at age 3! While brook trout populations suffer in the east, they have flourished in the west and are have wiped out native fish in some northern New Mexico water.

Clearly, this eradication process will not happen overnight.


One site of introduction of the YY Trojan brook trout is near the Colorado border in the Tusas Mountains of Northern New Mexico. Somewhere in the Carson National Forest, a small creek was found to have gold. By early in the 1880's, prospectors made significant gold strikes in the area. Mining activity began in the area as early as the late 1870's and by the 1880's over $175,000 worth of gold had been mined from the creek in 3 years. In 1903, an extensive hydraulic mining operation was set up in the gorge. Hydraulic mining is a technique of mining that uses high pressure jets of water to remove rock and sediment to expose gold veins, washing the gold to sluice boxes to be extracted. Hydraulic mining became popular in the 1850's during the California Gold rush and although successful, resulted in extensive environmental damage. The little creek was dammed and water was rerouted. I can only surmise that the Rio Grande cutthroat trout, and other creatures that inhabited the river at the time, fell victim to the destructive mining operations. Small scale mining was conducted in the area for decades. Perhaps that is the reason that brook trout were introduced to the creek from the east. Eventually, the town, which even had a post office from 1894-1906, disappeared and the creek was dammed for the final time creating a recreational lake. The tiny little stream that flowed through those claims, as well as the lake, is full of tiny brook trout (as well as rainbow trout) today, I can imagine that at the time of the early gold strikes that water would have been filled with Rio Grande cutthroats and hopefully will be again someday soon with the help of the Trojan males.

Although still in the early stages of implementation and research, this management tool might be what is needed to restore native fish populations in Northern New Mexico and across the west. I have been in contact with NMDGF for information given in this blog and will hopefully write a follow-up in the future on the progress of the program.

Let me know your thoughts!

Do you think this program will be successful? Should brook trout stay in the west?


Rio Grande Cutthroat Trout

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Love your perspective on the unintended consequences that got us here and the scientific efforts that may get us back


Lynn Decker
Lynn Decker

Great post.

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