Scientists hope to glean wealth of information about Canyon species<br>

Intensive monitoring and mapping before and after high flows will help to better understand early life stages of humpbacks and how short- and long-term changes in their habitat relate to fish survival.

Scientists will conduct a hoop-net survey to examine the effect of the flow on juvenile humpback chub near the confluence of the Little Colorado River.

Recent surveys showed a high number of juvenile chub in this reach. The 2004 reproduction year yielded some of the largest catches of young-of-the-year chub in many years.

It is hypothesized that because the chub evolved under the highly flood-prone conditions of the Colorado River, they will not be negatively affected by this experimental high flow, but this needs to be tested to be sure.

The U.S. Fish and Wildlife Service listed the humpback chub as an endangered species in 1967. Critical habitat was designated for portions of the Colorado, Little Colorado, Green and Yampa rivers in Arizona, Colorado and Utah.

In the Lower Colorado River Basin, a large humpback chub population occurs in the Grand Canyon. In the Upper Colorado River Basin (above Glen Canyon Dam), the largest populations occur in the Colorado River near the Colorado-Utah border and in Desolation/Gray canyons on the Green River in Utah. Smaller populations occur in the Yampa River in Colorado and Cataract Canyon on the Colorado River in Utah.

Another part of an overall experiment to test the effect of flow and non-flow actions that enhance and restore natural resources in the Canyon involves the removal of non-native fish from a critical habitat for the endangered humpback chub near the confluence with the Little Colorado River. While unrelated to flows, this research effort will continue in concert with the overall research design.

Non-native rainbow trout, a predatory species, are an important resource for anglers below Glen Canyon Dam in the first 15 miles, to Lees Ferry. Surveys to determine the relative abundance of trout were recently completed by the Arizona Game and Fish Department. These surveys will be repeated in mid-December to determine the effect of the high flows on trout populations and trout diet.

Another endangered species, the Kanab ambersnail, is the focus of an experiment to determine if its habitat can be protected from experimental floods. As a result of mitigation for previous experimental flows, agencies have successfully established an additional endangered Kanab ambersnail population at Upper Elves Chasm.

At Vasey’s Paradise, up to 120 square meters of the ambersnails’ monkeyflower habitat may be lost due to high experimental flows. Therefore, up to 48 square meters of that vegetation habitat has been removed by hand – similar to sod-cutting – stacked on pallets and moved above the flood.

After the high flow ends, the vegetation will be relocated to the flood zone, and growth hormones will be applied to plants to encourage re-establishment of snail habitat.

The aquatic foodbase is important for all species living in the river. A fundamental component of the foodbase is “drift” or the floating array of invertebrates, algae and other bits and pieces of raw material carried down the river as a result of the natural erosion of the channel and surrounding landscape. Drift provides a source of energy and carbon to higher organisms, including fish.

Drift samples will be taken below the Little Colorado River to determine changes in the foodbase before, during and after the flood. Pre- and post-flood surveys of algae and aquatic vegetation beds, an important part of the foodbase, will also be conducted in the Lees Ferry reach.

Researchers will also study the effect that the flows will have on restoring plant growth favorable to the endangered Southwestern willow flycatchers.

Previous experimental flows resulted in sediment deposition that promoted growth of riparian vegetation favored by flycatchers, who build their nests along Southwestern rivers during the summer months. The Lower Colorado River has been proposed as critical habitat for the flycatcher.

Scientific studies will continue after the high-flow experiment to examine the condition and status of sediment deposited on the beaches and the long-term effect on the natural and cultural resources.

The current experimental flow of 41,000 cfs will not have a direct adverse effect on additional historic properties. In fact, researchers expect that the indirect effects on historic properties will be positive. The intention of the flow is to redistribute sediment onto the terraces (beaches, sandbars) and into drainage channels adjacent to the river.

This operation should raise the river’s current base level and increase the amount of fine-grained sediments available for eolian (wind) transport, which will enhance the upper terraces and infill the drainage channels. These processes are necessary for the preservation of historic properties.

Cultural resources that would be improved indirectly by this test flow include historic properties (sites eligible for listing on the National Register of Historic Places). These sites date mainly 1000 to 1200 A.D. and represent the Cohonina and Puebloan cultures (modern Pueblo Indians (Hopi and Zuni) and ancestors to the Hualapai, Havasupai and Southern Paiutes.

Other cultural resources include Traditional Cultural Places and sacred sites, including springs, specific geographical locations for mineral collections, and plant- collecting areas. These are important to the tribes’ cultural affiliation to the Canyon.

Regarding effects on beaches, the size, abundance, and distribution of the sand deposits that serve as campsites limit the river’s recreational carrying capacity within Grand Canyon National Park.

The high-flow experiment is designed to deliver sediment that has been deposited into the Colorado River from the Paria River and other tributaries to higher elevations, thus rebuilding camping beaches and improving recreational opportunities.