By Owen Woods | owen@alamosacitizen.com
THE Rio Grande cutthroat trout is the Rio Grande National Forest’s only native trout. It needs help. Biologists from Colorado Parks and Wildlife and Rio Grande National Forest are trying to bring the cutthroat back to its full glory, but they need help, too. So who do the humans look to for help?
Easy answer: Beavers.
Jason Remshardt, wildlife and fisheries program manager for the Rio Grande National Forest, recently gave a presentation on the Rio Grande cutthroat trout. He is the only fish biologist in the RGNF. He talked about the effort to create and conserve habitat for the cutthroat, and how the answer might just come from nature’s finest engineers.
The Rio Grande cutthroat trout used to exist in just about every part of the Rio Grande basin, but due to a wide range of circumstances, these fish only occupy a fraction of the area they used to. Part of conservation and successful reintroduction is habitat restoration. Right now, the experts are looking at nature’s experts. These projects are imitating “what the beaver dams are doing,” said Remshardt.
These “Beaver Dam Analogues” or “Temporary Wood Grade Structures,” or TWGS, (pronounced like twigs), are designed to help back up water and create a lively wetland habitat that encourages healthy biodiversity not just for the cutthroat, but the entire ecosystem.
They are being employed in what’s called “Process-Based Restoration.” These man-made structures are relatively easy and straightforward to make. They are built with natural resources such as wooden posts, willow branches, aspen branches, and rocks.
Though they are simple to create, Remshardt said “we’re not as good at building them” as the beavers.
“It’s a technique that’s become increasingly popular across the western U.S. within the last few years,” said Connor Born, project manager for the Rio Grande Headwaters Restoration Project.
The man-made structures can help to create a more complex habitat that encourages a healthier fish population. Born says that this can mean “deeper pools that serve as low-flow refuge and slower moving water for younger fish. The structures can also benefit surrounding vegetation, provide fire breaks, increase stream shading, and grazing forage.”
Cutthroat trout populations often live in smaller streams that don’t have much water. According to Born, “The structures can help attenuate water in these smaller streams to provide more consistent flow and temperature during periods of drought.”
Cat Creek near La Jara Reservoir once had populations of the cutthroat and beavers. For unclear reasons, the beavers left that area. Their departure, Born says, “paired with prolonged drought conditions, caused flows to become much more intermittent, eventually leading to the suspected die-off” of the cutthroat trout population there.
So far, the groups undertaking this project have implemented 10 of these structures in the Rio Grande National Forest. Remshardt noted that “if they last for a few years, that’s great. If the beavers take them over, that’s great. If they disappear, then you haven’t lost that much. You’ve just lost like half a day’s work.”
According to Born, the first 10 structures are in the headwaters of Saguache Creek in Saguache Park. There are 12 more ready for construction in the coming year that will be built along Big Springs Creek, a cutthroat stream near Saguache.
Born said that the restoration structures can function without beavers, but the organizations are hoping to find places where the two can combine forces.
Beavers in the national forest are alive and thriving. Remshardt says that the RGNF is happy with current populations, but there is room for expansion and improvement. With that, the benefits of beaver dams create healthy, expansive wetlands. Beaver dams and habitats also make great fire breaks.
These animals, however, are considered a nuisance species to certain areas of the Valley. Beavers can be troublesome to infrastructure like irrigation canals and roads.
“There’s this stark contrast of existing as a pest species on the Valley floor while being highly beneficial up in the headwaters. The logical solution,” Born said, “is an efficient, legal, and humane way to translocate them to areas where their engineering is more appreciated and doesn’t impact infrastructure.”
Relocating the beavers pairs well with the restoration efforts. Born said that the structures may encourage beavers to stay in areas that “have habitat that would otherwise be too degraded.”
Remshardt says there’s plenty of space to relocate any problematic, or displaced wood-chopping rodents.
“We’re ready to take them and we have places all over the forest to take them. Plenty of places we can put them,” Remshardt said.
Identifying where beavers are and where beavers aren’t is a part of the job that requires a lot of work from a lot of people. Software like iNaturalist allows anyone to report animal sightings and tracks to help in identification. These reports can help biologists like Remshardt identify populations and locations to help further studies and surveys.
Helping the beavers help us really boils down to, Remshardt said, the fact that “beavers are the best at doing their own work.”
Surveys and History
The largest effort for studying these fish are surveys. Remshardt said they conduct surveys on every population of RGCT about every five years. These surveys cover at least 40 streams in the national forest and take a large number of people to conduct. The surveys gather the number of fish and their sizes, take genetic samples, and conduct health surveys.
Most of the streams and lakes are easy to access, but the Rio Grande Cutthroat Trout lives in the alpine, too. Remshardt said almost every drainage and lake in the Sangre de Cristo mountain range has cutthroat populations. So, in order to keep these high mountain lakes stocked and healthy, they conduct High Mountain Lake Airplane Stocking. A video from CPW shows just how these operations are done.
Conservation of the cutthroat, Remshardt said, remains the most intensive and expensive project. Ongoing research for more cutthroat introductions to expand them into their historic ranges is an ongoing and expansive effort. Currently, an effort to successfully reintroduce the cutthroat to the Sand Creek drainages at the Great Sand Dunes National Park is taking place. The project first started in 2005.
A blog post by Trout Unlimited’s Rio Grande Basin project manager Kevin Terry breaks down the history of this project. You can also read the USGS’s in-depth report on this effort here.
CPW estimates that the RGCT occupies just 12 percent of its native habitat. Biologists estimate that 127 “conservation populations” exist in Colorado and New Mexico. The cutthroats’ range has seen a dramatic decrease over the last 150 years. Some of the factors that have led to this decline are habitat changes, climate change, drought, water quality, hybridization with non-native Rainbow Trout and other cutthroat trout species, as well as aggressive competition from Brown and Brook trout.
Evidence suggests that the cutthroat trout thrived in healthy populations in Lake Alamosa, a lake that existed for over three million years.
The Rio Grande Headwaters Restoration Project, US Forest Service, Colorado Parks and Wildlife, and Trout Unlimited “are hoping to identify both at-risk RGCT populations and future locations for reintroduction and enhance the habitat using these restoration techniques,” Born said.