Rio Grande Cutthroat Trout

Rio Grand Cutthroat Trout

Oncorhynchus clarki virginalis

The Rio Grande cutthroat trout is New Mexico’s state fish. They also hold the distinction of being the southernmost subspecies of cutthroat trout. They are brilliantly colored and, depending on who you ask, are considered one of the prettier of the Cutthroat Trout.

What Do Rio Grande Cutthroat Trout Look Like?

These beautiful fish generally have tan to bronze-colored sides, transitioning to more brilliantly colored brass-colored backs. They have scattered black spots along their sides that are most abundant on and close to the tail and less so the further up the body towards the head you go. Most of them display red or orange coloration along their lower flanks. Universally they have the red slash on each side of the throat that is a distinguishing trait of all the Cutthroat Trout subspecies.

These fish primarily inhabit mountain streams. Due to the non-nutrient dense condition of these waters, these fish generally have a top size of 10 to 12 inches.

Rio Grande cutthroat Trout Habitat

These fish live at high altitudes, generally at 8000 feet or higher. They live in small streams that are clean, cold, silt-free with a moderate gradient.

They feed primarily on aquatic insects and nymphs as well as terrestrial insects. When the opportunity is there, they will also feed on small fish.

Rio Grande Cutthroat Trout Range

Today the Rio Grande Cutthroat Trout only occupies ten percent of its presumed historical range. Their current range consists of a few isolated lakes, rivers, and streams in the headwaters in the Rio Grande, Pecos, and Canadian river drainages in southern Colorado and New Mexico.

Historical Range

The first written account we have of Rio Grande Cutthroat Trout came from Spanish explorers in 1541. It’s the general consensus that they historically inhabited all waters within the Rio Grande, the Pecos, and the Canadian River systems capable of supporting trout. There is also antidotal historical evidence that these fish occurred as far south as Texas.

The Pecos River is a tributary of the Rio Grande. On The other hand, the Canadian River runs to the Mississippi and has no communication with the Rio Grande or the Pecos. Biologists believe that in some bygone era, the Canadian and Pecos rivers must have shared headwaters. This scenario explains the presence of the Rio Grande Cutthroat in the Canadian River drainage.

The Rio Grande Cutthroats in the Pecos and Canadian River drainages have been isolated from those in the Rio Grande for a sufficient amount of time so that they possess minor genetic differences.

Threats to Rio Grande Cutthroat Trout Populations

We’ve lost historical populations of these fish in the last 150 years due to the introduction of non-native fish into their domain, stream dewatering caused by irrigation diversions, dams, stream bank degradation due to overgrazing of livestock, whirling disease and natural cataclysmic events such as drought and forest fires. All of these threaten to have a limiting effect on diminishing Rio Grande Cutthroat Trout Populations.

Whirling disease

Whirling disease is a relatively new threat to native trout populations. This is a disease caused by the Myxobolus cerebralis parasite. It is a disease that effects all salmonid species to some degree. Native species are especially susceptible to this European origin parasite since they have not evolved alongside it as the Brown Trout has. Planted nonnative trout are a threat to native populations due to the possibility that they might be carrying whirling disease.

Non-native fish

The single most damaging factor to the native Rio Grande Cutthroat Trout population’s future viability is the introduction of nonnative fish into their historical range.

In the past, well-meaning fisheries management officials introduced Rainbow Trout, Brook Trout, Brown Trout, and Yellowstone Cutthroat Trout into the native range of Rio Grande Cutthroat Trout. In doing this, their intention was only to provide anglers with more fishing opportunities. They likely accomplished their goal. However, in the process, they did grave damage to the native Rio Grande Cutthroat trout population.

Rainbows, Brookies and Brown Trout are more aggressive than the native Rio Grande Cutthroat Trout. Consequentially, they outcompete them for food as well as prey on their young.

Rainbow Trout spawn at the same time as the native Rio Grande Cutthroat Trout and readily crossbreed with them. Yellowstone Cutthroat Trout do as well. From there, the resultant hybridized fish render Rio Grande Cutthroat Trout breeding populations ineffectual.

In cases where Brown Trout share habitat with Rio Grande Cutthroat Trout, Brown Trout become the dominant species. This is because they’re more challenging to catch. Fishermen harvest a greater percentage of Rio Grande Cutthroat Trout than the more elusive Brown Trout. In turn, the more numerous Brown Trout have a greater opportunity to propagate and fill in the population gap.

Stream dewatering

According to all the information I can find on the subject, stream dewatering due to human development and drought has been a detrimental factor to Rio Grande Cutthroat Trout populations. However, there isn’t a lot of credible research out there on the subject. Obviously, though, when we divert water for the needs of humanity, there is a resultant effect on the historical habitat.

Overgrazing of livestock

Again, there isn’t much research out there specific to Rio Grande Cutthroat Trout. Bearing this in mind, I’m going to give my take on the subject at the risk of offending some of you.

I come at this subject as a proponent of livestock grazing on public lands. Properly managed livestock grazing improves the condition of the range. Additionally, it utilizes what would otherwise be a wasted resource. However, grazing livestock in riparian zones eliminates streamside vegetation, which increases water temperatures and promotes the siltation of stream beds. It also eutrophies the water to some degree with livestock effluent. All 3 of these things are very bad for healthy cutthroat trout habitat.

Recovery and Conservation Efforts

The Seven Springs hatchery at Jemez Springs, New Mexico, concentrates on only one fish. They specialize in raising and rearing Rio Grande cutthroat Trout. To do this, they source genetically pure broodstock from populations throughout the state to produce fish to stock back throughout the state.

In New Mexico, significant effort has been put into removing non-native species from areas where this is practical and replacing them with the Rio Grande Cutthroat Trout that once lived there.

The Rio Costilla project is a prime example of this. In this one project, 120 miles of streams, 15 lakes, and 1 reservoir will have all non-native fish removed and replaced with Rio Grande Cutthroat Trout by the end of 2020. Additionally, terminal fish barriers will also be placed to prevent non-native fish from reaching areas set aside for Rio Grande Cutthroats.

In Colorado, the Hay press Lake is a primary collection point for Rio Grande Cutthroat eggs. The fish derived from these eggs are planted in waters throughout the Rio Grande drainage.

An example of the Rio Grande Cutthroat Trout restoration efforts ongoing in Colorado is taking place at Sand Creek in the Great Sand Dunes National Park. In this project, non-native fish are removed from 12 miles of Sand Creek and 2 lakes. Following that, these waters will be planted with native Rio Grande Cutthroat Trout.

This joint project involves the National Park Service and the following conservation groups. Running Rivers/Rocky Mountain Flyathlon, Trout Unlimited, and the Western Native Trout Initiative. It is slated for completion on September 30th of 2022.

Final Thoughts

The Rio Grande Cutthroat Trout is an integral part of our heritage in the western United States. If we lose them, it will only be through our neglect. The Federal government has reviewed their case on a couple of different occasions and determined each time that there is not yet sufficient cause to include them on the endangered species list. Let’s keep it that way.

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