We are standing in a rancher’s field. Algae and sediment give the water the turbid look of a bluegill pond. The distant trees may be a mirage in the 100 degree heat. Dust floats off the ground like anthrax. And yet, this beautiful cutthroat, one of the largest I’ve ever seen, calls this place home.

Well actually, this fish is just passing through. Bonneville cutthroat are marvelously adapted for surviving in the harsh, semi-desert conditions of the Bear River system. The Bear River drains the intersection of Wyoming, Idaho, and Utah on its way to the Great Salt Lake. It is tough country for trout and people alike. Migration is one of the characteristics that allows this species to thrive here.

The adult Bonneville cutthroats feed in the main river, growing large on a diet of forage fish. Some individuals exceed 24 inches and 20 inchers are relatively common. Then, in the spring, they migrate upstream into the headwaters. Some individuals move 90 kilometers. The Bonnevilles spawn in the small tributary streams, where their young hatch in a cooler and safer environment than the Bear River proper. After a couple years in the headwater streams, many of the surviving offspring will migrate to the river in search of forage, continuing the cycle.

Until just a few years ago, no one really knew how far these fish were traveling. Warren Colyer’s master’s project shed light on the annual migrations of these amazing fish. Today, Warren works for TU, coordinating a recovery and monitoring effort for the Bear River Bonneville.

The Bear River Bonnevilles face an uphill battle. Water is a limited commodity in the basin and the rivers have been dammed and diverted for over 100 years. These obstructions were not constructed with fish passage in mind and the migratory routes to essentially every tributary were affected.

Migratory fish entering the tributary rivers, such as the Thomas Fork, are stuck between a rock and a hard place. In dry years, the irrigation diversions are in operation during the spawning run, and the headgates block migration entirely. If it is a wet year, fish make it past the gates before irrigation has commenced, but almost 50% of the fish will get stuck in the irrigation ditches and die on their post-spawn journey back to the Bear River.

After a century and a half of neglect, the migratory Bear River Bonneville population is hanging on by a thread. Fortunately, TU hired Warren to continue his study of this amazing fish. His objectives are to both gain a better understanding of the species and implement solutions to give them a leg up.

In just the last few years, Warren has worked with landowners to construct fish screens on three irrigation ditches in the Thomas Fork. The screens allow the ranchers to take the water they need for irrigation, but prevent fish from getting trapped in the ditches.

Last year was the first season that all three screens were operational. The results? An increase from 6 Bonnevilles observed in the stream to 200 in just one year! A true scientist, Warren modestly points out that better water flows were probably a contributing factor, but this figure is certainly a good indicator that the screens are helping the Bonneville spawning run.

The Smith’s Fork of the Bear is the last tributary to hold a healthy run of Bonnevilles. In fact, in dry years when fish have been turned away by the diversions on the Thomas Fork, Warren has tracked them over 75 kilometers up the Smith’s Fork. This stream provides the migratory Bear River fish with the toehold they need to avoid extirpation.

Warren studies the Bonneville cutthroat in the Smith’s Fork and the Thomas Fork, providing an interesting comparison between a relatively pristine fish run and a stream in recovery.

Twenty-five miles from the nearest paved road, Adam Sepulveda and Warren Colyer are huddled over a metal box filled with wires and computer parts. I’ve often heard folks lamenting that kids spend too much time in front of computers and not enough time outdoors these days, but as we played with this radio-tracking antenna, I almost wished I had spent more time futzing with electronics when I was younger.

Thanks to Adam’s expertise, the whole operation went relatively smoothly. Adam is a PhD student at the University of Montana. Part of his project involves the Bear River Bonnevilles. Adam is looking at the ratio of different types of nitrogen and carbon in tissue samples to tell where in the river system a fish has been feeding. Hopefully, this research will lead to an easy, unobtrusive way to test if a fish is migratory. Somehow, Adam also knows about radio antennas.

Warren and his field technicians currently operate fish weirs on the Thomas Fork and the Smith’s Fork. With the weirs, hook and line sampling, and electrofishing, Warren and his crew capture Bonnevilles and tag them with P.I.T. tags, little radio transponders that are inserted into the fish’s belly (see the photos HERE). The P.I.T. tag gives the individual fish a code, allowing it to be tracked throughout the migration, or even year-to-year.

If the crew captures the fish again, they have a wand-like device that will detect the P.I.T. tag, allowing them to keep track of where and when this particular individual has been captured.

The radio-tracking antennas will ease this process considerably. The antennas automatically detect if a P.I.T. tag moves by and records the data in a palm pilot. The use of two antennas in tandem reveals which direction the fish is moving.

These slick devices are another tool that will not only make Warren’s life easier, but will also shed light on the time of migration for the Bear River Bonnevilles. Understanding when these fish move is a crucial piece of information when working to keep the fish out of the ditches.

After installing the first antenna, Warren, Adam, and I grabbed our fly rods and headed upstream. We alternated pools, casting streamers and hoppers to likely lies. The Bonnevilles were spread out and not every good cast produced a fish, but when one did chase the fly, it was certainly exciting.

These fish are ambitious. Their toothy mouths want a meaty meal. Warren likes to throw mouse flies towards dark, and even the 13” Bonnevilles will attack a small mammal imitation. We slipped P.I.T. tags into the fish that we caught, hoping that soon they would put the new antennas to the test.

Unfortunately, even the pristine Smith’s Fork is at risk. The state of Wyoming is pushing a proposal to construct a dam on this river that would effectively eliminate the last healthy run of large Bear River Bonnevilles.

Despite the fact that Bonnevilles currently occupy only 5%-30% of their original range and key populations (including the migratory fish in the Smith’s Fork) are at risk, the US Fish and Wildlife Service turned down a petition to list the Bonneville cutthroat under the Endangered Species Act in 2002.

The denial of federal protection and the proposed dam are just two new additions to a long list of assaults on the Bonneville cutthroat. Fortunately for the fish, Warren isn’t crying in his beer. He is studying their numbers and habits, working with landowners and government agencies, and doing what he can to help this incredible species.

Migratory Bear River Bonnevilles have survived for thousands and thousands of years in this inhospitable environment. I hope that we don’t squander their entire existence in a few short decades.

For photos of the 21”+ Bonneville, a 13-incher with a mouse fly in its mouth, as well as a glimpse of the scenic Smith’s Fork, CLICK HERE.