At a little known waterfall on a remote part of the San Juan River, more than a thousand endangered fish, previously unaccounted for, have been found in populations that are thriving – a potentially groundbreaking discovery.
“We assumed they were dead or lost to Lake Powell,” said Mark McKinstry, a research biologist for the Bureau of Reclamation. “Somehow, they adapted.”
Once widespread and abundant, the razorback sucker was listed as an endangered species in the early 1990s after being driven to near extinction by over-fishing, the introduction of non-native species and the installation of dams.
These pressures decimated razorbacks on the San Juan River, which starts in southern Colorado, flows through a sliver of northern New Mexico and down to its confluence with Lake Powell in Utah.
As a result, the San Juan River Basin Recovery Implementation Program was created to offset the impacts of water-use developments by re-establishing two impaired species of fish: the razorback and Colorado pike minnow.
As part of the recovery program, razorback suckers are raised in hatcheries and stocked in the San Juan River. Each fish is given a tag, much like those implanted in pets, to track its movements throughout the watershed.
This allows researchers to recapture fish and collect a variety of metrics about the success of stocking, such as population numbers, survival rates and migration habits.
Every year, about 10,000 razorbacks are stocked near Farmington, McKinstry said. However, it’s estimated that only 2,000 to 4,000 razorbacks live in the San Juan River below Navajo Dam and above Lake Powell.
But years ago, McKinstry’s attention was drawn to a unique and extremely remote waterfall on the San Juan River, upstream of Lake Powell and about 3 miles downstream of the Clay Hills take-out for boaters.
The waterfall – known as the Piute Farm’s Waterfall – is relatively new, created both by the rise of Lake Powell’s waters and their decline in recent years
When dams are built, rivers that flow into the reservoir deposit tons of sediment at the mouth of the delta. It’s estimated that sediment deposits in the San Juan River confluence area are about 80 feet thick.
But when water levels in reservoirs drop, as is the case at Lake Powell, the incoming rivers form new paths that cut through the deposited sediment.
The San Juan River’s original path is buried under this thick layer of sediment, about 3 miles away from where it now flows.
With Lake Powell’s water level falling, the San Juan River’s route is now through the sediment and over a bedrock cliff, forming a 20-foot waterfall.
The waterfall spans the entire river and is considered impassable by boaters going downstream. But it’s also impassable for fish seeking to go upstream.
For years, researchers thought that any razorbacks stocked in the San Juan River that passed over the waterfall simply went into Lake Powell to disappear and, in all likelihood, die.
That’s because researchers considered the razorback to be a sedentary fish that lived its life in rivers, McKinstry said. But that thinking started to change in the past few years.
In 2011, a research project on Lake Powell found a number of razorback fish in the lake, thriving.
“In fact, they were doing pretty damn well,” McKinstry said. “That reignited our thinking about what we could do.”
Working on a hunch, McKinstry suspected that perhaps razorbacks in Lake Powell were bottlenecked at the waterfall, trying to get upstream in the San Juan River to spawn.
But for years, the old methods of surveying fish populations didn’t work in the remote area where the waterfall is, either a 2½ hour drive from Mexican Hat, Utah, or a 100-mile boat ride from Bullfrog Marina in Lake Powell.
Then, a new take on existing technology allowed for a major breakthrough.
Peter MacKinnon, a research scientist at Utah State University, helped develop an antenna that, while fully submerged in water, can detect the tags placed on razorback suckers.
“All of a sudden, we were able to get information from areas where we couldn’t before,” MacKinnon said. “Until we could throw this (antenna) in there, those fish were a lost population up in the San Juan.”
McKinstry remembers the date of the “aha moment” when researchers knew the technology was a success: March 9, 2015.
The group took a trip down to the waterfall, where the new antenna had been placed two weeks earlier. In that time span, the antenna tracked more than 450 endangered razorbacks, McKinstry said.
Over a three-year period, from 2015 to 2017, nearly 1,500 razorback suckers were detected downstream of the waterfall – a momentous number considering the overall population is estimated at 2,000 to 4,000 fish, McKinstry said.
And the discoveries just kept coming.
Through the tagging system, researchers found some razorbacks at the base of the San Juan River waterfall originated in the White and Gunnison rivers, a colossal voyage down the Colorado River and across Lake Powell.
“That’s a 500-, 600-mile trip for a fish up until now we thought was fairly sedentary,” McKinstry said.
The antenna was even able to discover populations of another impaired fish, the Colorado pike minnow. Their numbers were fewer, however, likely because they are too small to be tagged when they are released into streams.
The research findings will have a resounding impact on the future management and conservation efforts for the razorback, McKinstry said.
Razorbacks are usually capable of reproducing on their own. The big issue, instead, is surviving from the larvae to adulthood stage.
The only known self-sustaining population of razorbacks is located, ironically, in Lake Mead, McKinstry said.
This discovery of healthy, adult razorbacks bottlenecked at the base of the waterfall is leading researchers to believe the fish are trying to get upstream into the waters of the San Juan River to spawn.
“We’ve figured out these fish know how to make a very good living in the lake,” McKinstry said. “But then they want to travel back upstream to spawn … and there’s a lot of fish excluded from the spawning process.”
But there are serious implications when considering creating a fish passage or removing the waterfall.
Removing the waterfall would allow the razorback and other native fish renewed access to the San Juan, and it could create a channel for future sediment flows farther downstream.
On the other hand, removing the blockade could also allow a whole new batch of invasive species, such as channel catfish and small mouth bass, into the upper reaches of the San Juan.
Casey Pennock, a doctoral student in the division of biology at Kansas State University who took part in the research, will take the findings a step further, analyzing how fish have adapted to living in Lake Powell.
Fish, which once could travel freely from Baja California to the Colorado Rocky Mountains, have a whole new underwater landscape to navigate, and understanding how they survive is important to keeping them alive, he said.
“It’s really difficult to wrap your brain around what these fish used to have access to,” Pennock said. “Now with their numbers up, we need a further understanding of how they interact with an altered environment.”
While a lot of research has gone into environmental impacts below dams, in recent years, attention is turning to what happens upstream, Pennock said.
“It’s more important than ever to keep that research going,” he said. “Because we’re making new discoveries about things we thought we understood, every day, and that’s fascinating to see.”
Ultimately, whatever research is gained, is gained in the pursuit of one goal – to have self-sustaining populations of razorbacks, McKinstry said.
“From a management agency standpoint, this is a huge deal,” he said. “We not only found a (expletive) load of fish below the waterfall, we found some travel great distances.”
jromeo@durangoherald.com
