BLM Colorado

BLM Colorado

Wednesday, June 14, 2017

Rio de Nuestra Señora de los Dolores “The River of Our Lady of Sorrows”


Rio de Nuestra Señora de los Dolores “The River of Our Lady of Sorrows”:  BLM Colorado’s Southwest District Lower Dolores River Survey Trip

The diverting of water in the Montezuma Valley from the Dolores River started in November of 1885, when construction of the 5,400 foot Montezuma Valley Water Supply Company Tunnel through the Dolores Divide began. But, as the area and the demand for water grew, extra canals were built that helped provide water to more people. But, the canals carried too little water and shortages scourged the farmers and residents in the valley. On November 20, 1961, the Dolores Water Conservancy District was formed and in 1968 the project for McPhee Reservoir was approved. However, the project wouldn’t start until 1977 and was not completed until 1984. After two years of closure, the reservoir had filled by 1986. The project cost an estimated $500 million, along with an $11.6 million Dolores tunnel that was dug underground from Big Bend to Cortez. The construction of the dam also created a need for pumping plants, canals, and two recreation areas. The now filled reservoir sits where a bustling logging town once resided, McPhee, along with numerous archaeological sites. The artifacts found at these sites needed a place to be housed. So, the Anasazi Heritage Center was built to house those artifacts and is managed by the BLM’s Tres Rios Field Office.

Celene Hawkins paddles ahead of the chase boat through Slickrock Canyon (Photo: Russ Japuntich, BLM)

The Dolores River is home to three native warmwater fish, the roundtail chub (Gila robusta), flannelmouth sucker (Catostomus latipinnis), and bluehead sucker (Catostomus discobolus). The dam’s completion added additional in-stream flow alterations, a coldwater fishery below the dam, and the successful introduction of other warmwater species; these additions have resulted in the decline of native fish and will prove to be focal points for future management and native fish success. The need to manage the Dolores River below McPhee because of the aforementioned additions and the protection of native fish created a working group called the Lower Dolores Plan Working Group-Legislative. Their main objective is to gather and summarize information that will describe the status and trends of native fish and is divided into two phases.

          Phase 1: Describe the status of the three species in the Colorado River basin, describe the status of the three species in the Dolores River between McPhee Dam and the confluence of the San Miguel River, describe potential reasons for population changes in the Dolores River, and describe preliminary management options and opportunities for improvement of the Dolores River fish community.

          Phase 2: Use the summaries of fish status in the study area from phase 1 reports and then formalize the presentation of opportunities for improvement for the fish community; main topic areas include spill management, base flow and fish pool management, each of which include aspects of thermal regime management, and reduction of effects of non-native fishes.

CPW Biologist Jim White holds a large flannelmouth sucker.
A nice roundtail chub.

CPW Biologist Eric Gardunio displays the easily identifiable mouth of a bluehead sucker, with its very pronounced scraping ridge. (Photos: Jim White, CPW)

The life history of these species have some general similarities, but are relatively unique. Spawning for flannelmouth and bluehead suckers occur in late spring as flows begin to rise from runoff and roundtail chubs occur as the flows begin to decline, early summer. Spawning during runoff is key, because the high flows disturb and move substrate and flush fine sediment from rocks, which ensures clean substrate for spawning. After spawning and embryo development take place, the larvae emerge and begin to drift downstream. Larvae will drift until they come across areas of low to zero velocity, which happen to occur in pools and backwaters. These slow water habitats are important to the fish larvae because chironomid larvae also utilize these areas and are an important food source. This habitat is also advantageous because water temps are fairly warm, which increases growth rates in the fish. As the fish advance into their juvenile life stages, their habitat dependency and diets becomes more specialized. Bluehead suckers occupy swift riffle-run habitat, flannelmouth suckers occupy run and pool habitat, and chubs occupy pool and backwater habitat.

BLM Fish Biologist Russ Japuntich, keeping a lofty eye in front of the boat for surfacing fish with his net in hand, instead of taking in the scenery. (Photo: Jim White, CPW)

The three species were once abundant throughout the Colorado River Basin and present in cool and warm water reaches of small to large streams. They now occupy 50% or less of their range in the entire Colorado River Basin and only 45 – 55% of their range in the upper Colorado River Basin. The decline in the species is likely due to flow modifications and the establishment of non-native species. Non-native species in the system pose a problem through competition and predation. The greatest non-native fish threats are trout in the cold water reaches below the dam and smallmouth bass in the lower and warmer reaches. The white sucker is another potential threat to the native fish, due to its ability to hybridize with bluehead and flannelmouth suckers; resulting in loss of genetic integrity of native catostomids. White suckers are present above the dam and in other streams throughout the upper Colorado River Basin, however none have been documented in the Dolores downstream of the dam. White suckers and their hybrids are difficult to manage and the establishment of them in the system should be avoided. Although, other non-natives are present in low abundance and are not currently a threat; but may become one under different environmental conditions.

Leech Creek at the confluence with the Dolores River (Photo: Celene Hawkins, Nature Conservancy)

Altered in-stream flow and temperature regimes can also play a factor in the decline and success of not only native fish, but also non-natives. Dramatic alterations in flow and temperature can affect the maturation of gonads in fish and recruitment success. Early warming periods can cause the maturation of gonads to occur earlier, then if spawning and emergence takes place prior to high flows; earlier life stages of the fish are likely to experience high mortality. These high flows of cooler water before or after hatching can also limit hatching success of the fish and growth rates. However, utilizing the drastic changes in flow and temperature could also help in reducing non-native fish spawning and recruitment success.

The focal point of the survey consists of the stretch through Slickrock Canyon, which encompasses 32 miles of the Dolores River from Big Gypsum Valley Bridge to Bedrock (figure 1). The canyon is full of beautiful scenery consisting of towering canyon walls and overhangs that have been carved out overtime by fluvial processes. The last time this stretch was surveyed via raft was in 2007. Each of the three species were captured during the survey, however they were in low abundance. Very few non-natives were present, many of which were channel catfish and common carp; both of which do not pose as a huge threat to native fish. It was also noted that there was a large number of young-of-year native fish near the mouth of Coyote Wash, hinting at the importance of these tributaries as areas of recruitment.

CPW Native Fish Biologist Paul Jones and BLM Fisheries Technician Josh Ryan look to net some fish under an overhang. (Photo: Jim White, CPW)

Fast-forward ten years to Sunday, May 14, 2017 as we arrive at the put in at Big Gypsum. The survey was a cooperative effort with the Bureau of Land Management, Colorado Parks and Wildlife, and the Nature Conservancy. We spent the first afternoon unloading and preparing the rafts for an early start the next day, organizing, double checking equipment, and answering questions posed by groups of rafters floating by or launching. The survey trip was supposed to have lasted four days (not counting Sunday), but due to incoming weather we worked quickly and completed the 32 mile stretch in 3 days. Sampling of the river was completed using two electrofishing rafts, outfitted with two booms on the front of the raft. Each raft picked a side of the river and surveyed that side for the entire trip. Behind the electrofishing rafts there was a chase boat, a gear boat, and a duckie raft that stayed behind and surveyed the major tributaries to the Dolores at their confluences. All fish that were captured during the survey were measured and weighed; while native fish were also scanned for PIT tags, and if one was not present, the fish was tagged and the tag number recorded.

During the course of the survey, over ~400 native fish (all three species identified) were captured and tagged; a few of which were recaptures that had been tagged in previous years by other biologists. Judging by the fish that were captured, species compositions and size distributions had not changed since 2007. Other species captured was speckled dace (Rhinichthys osculus, native) black bullhead (Ameiurus melas, non-native), green sunfish (Lepomis cyanellus, non-native), fathead minnow (Pimphales promelas, non-native), brown trout (Salmo trutta, non-native), and white sucker (Catostomus commersonii, non-native); as of right now this is the first documented white sucker in the Dolores. Similar to the previous survey in 2007, a lot of juvenile fish were documented. Except they were scattered throughout the whole reach, which was promising even though it seemed there was a lack of backwater habitat to support larval recruitment.

White sucker (Catostomus commersonii), possibly the first one documented in the Slickrock Canyon. (Photo: Paul Jones, CPW)

Scanning a flannelmouth sucker for a PIT tag. (Photo: Paul Jones, CPW)

Overall, the trip served a great purpose, it allowed the fish biologists an opportunity to see what is going on with native and non-native fish assemblages throughout the canyon. Sampling through the canyon was tough due flows hovering around 800 cfs and the water being fairly turbid. Catch rates were low, so sampling data will be used to determine species composition and CPUE (catch per unit effort). The trip also allowed those with hydrology and other backgrounds a chance to see how these large flushes have affected river morphology, sediment deposition, and riparian zones. As mentioned early in the blog, a less than ideal forecast caused us to speed things up the last day and rightfully so. We were greeted the first few days on the river by warm, clear, and sunny skies. But, the last day the Dolores gave us a pleasant gift with a group of desert bighorn ewes and lambs across river from us, whom we had watched the evening before as they moved along the ridgeline of the mesa. But, the tone quickly changed and the river made it known we had overstayed, with a farewell of cold temps, wind, rain, and finally a spring snow storm as we headed home.

Desert bighorn sheep from across river the final morning. (Photo: Celene Hawkins, Nature Conservancy)

A less than ideal way to end a raft trip in the middle of May, but that is spring in the Rockies for you. (Photos: Jim White, CPW)

PW Native Fish Biologist, Paul Jones, paddling through the home stretch. (Photo: Jim White, CPW)

Views from the first night at camp on the river. (Photo: Josh Ryan, BLM)