Freshwater Fishing News

Natural stream flow suits native trout populations best, according to a study that examines the impacts of dam operations on threatened freshwater trout. The study appears in River Research and Applications.

In a study to identify the potential impacts of Hungry Horse Dam (Montana) operations on declining native trout populations, scientists with the U.S. Geological Survey, Miller Ecological Consultants, Inc., Spatial Sciences & Imaging and Montana Fish Wildlife and Parks examined how changes in river flow affect fish habitat on the upper Flathead River in Montana.

“Our research suggests past flow management practices created sporadic flow fluctuations that were likely detrimental to threatened bull trout and westslope cutthroat trout populations in the upper Columbia River Basin,” said Clint Muhlfeld, project leader and USGS scientist. “With Montana providing 40 percent of the U.S. water storage in the Columbia Basin Power and Flood Control system, water demands –and biological impacts—are significant.”

Populations of native bull trout and westslope cutthroat trout have declined throughout ranges in western North America due to a many factors, including habitat destruction, fragmentation and non-native species. Dam operations in the Columbia River Basin have contributed to these declines by changing flow and habitat, and disrupting routes of fish migration.

Loss of habitat connectivity and habitat modification can be especially detrimental to native trout populations, the study found. These fish migrate to spawn and feed and prefer large, relatively pristine habitats that are connected without any barriers such as dams.  Although the upper Flathead River system in Montana and British Columbia, Canada, is considered a regional and range-wide stronghold for bull trout and westslope cutthroat trout these populations may be threatened by the effects of 55 years of altering flow downstream of the Hungry Horse Dam.

Results of the study further suggest that dam management strategies that are more similar to the natural flow of the river will likely improve the chances of protecting habitat and help to maintain and restore bull trout and westslope cutthroat trout populations.

“Analyses comparing the natural flow of the mainstem Flathead River (predam, 1929–1952) with five postdam flow management strategies (1953–2008) show that natural flow conditions optimize the threatened bull trout habitats and that the current management practices best resemble the natural flow conditions of all postdam periods,” Muhlfeld said.

One caveat to this observation, said Muhlfeld, is the practice of increasing flow in the late summer to help fish species such as salmon and steelhead, known as “anadromous” because they migrate from salt water to fresh water to breed.  According to the study, increasing flow to benefit one species is actually reducing the amount of suitable habitat for another – the bull trout, a species listed as a threatened under the Endangered Species Act.

“Several studies have shown that dam operations have profound effects on anadromous fishes, yet before ours, few studies have examined the impacts of flow management strategies on habitats of threatened, native trout species in the upper Columbia River Basin,” Muhlfeld said.

Results from the study are featured in the April 2011 early online edition of River Research and Applications.  The article is titled “Assessing the impacts of river regulation on native bull trout (salvelinus confluentus) and westslope cutthroat trout (oncorhynchus clarki lewisi) habitats in the Upper Flathead River, Montana, USA” and can be viewed online.

source: USGS

In an effort to improve the fishery in Colorado’s Animas River through Durango and the Southern Ute Indian Reservation, three agencies are working to stock 100,000 rainbow trout in the river annually.

In early July, the Colorado Division of Wildlife and the Southern Ute Indian Tribe spread the fish in the river from Santa Rita Park in Durango to Bondad about 16 miles south of Durango. The fish were 5-6 inches in size.

The fish stocking is paid for by the U.S. Bureau of Reclamation as mitigation for the removal of water from the Animas River to Ridges Basin Reservoir, also known as Lake Nighthorse. An agreement on a stocking and monitoring program was developed by the BOR, the Southern Ute Tribe and the DOW.

The fish are being raised at the U.S. Fish and Wildlife Service national fish hatchery in Hotchkiss. An additional 50,000 trout, 10 inches in size, will be raised at the hatchery and stocked annually in the reservoir. Stocking in the reservoir will start this fall.

The stocking and monitoring of the fish will be performed by the DOW and the Southern Ute Tribe.

“We are really excited about the agreement because everyone gets something out of the deal,” said Jim White, DOW aquatic biologist in Durango, “The Southern Utes get a healthier fishery, we get stocking extended into the Gold Medal reach of the Animas River, and the BOR gets some of their environmental commitments covered through our fish survey work.”

The agreement will enhance the cooperative efforts of the tribe and the DOW in maintaining a healthy fishery in the Animas River.

“The agreement allows all parties to decide how best to manage these stocked trout using the information gathered during our coordinated fish surveys,” said Steve Whiteman, director of wildlife resource management for the Southern Utes. “If our current stocking parameters are off in some way, there is now a formal mechanism in place to address problems and do what is best for the resource.”

As stocking efforts continue every year, more and more of the fish stocked will be the whirling-disease resistant strain of rainbows that are being developed by DOW at its hatcheries. Aquatic biologists hope that those fish will begin to reproduce naturally in a couple of years. This is the second year that fish have been stocked in the river.

DOW and Southern Ute biologists will conduct surveys in the river to determine how many of the stocked fish are surviving.

The BOR began pumping water from the Animas River into the reservoir in 2009. Agency officials expect that the reservoir will be filled to capacity by mid-summer 2011.

source: Colorado Division of Wildlife

Agriculture Secretary Tom Vilsack and Interior Secretary Ken Salazar have announced joint scientific research projects that address the effects of climate change on freshwater systems and sensitive aquatic species in the northwestern and southeastern United States.

“Addressing the challenges of climate change will require new tools that enable our leaders to develop successful strategies,” said Vilsack. “This research will provide tools and information to help ensure that aquatic ecosystems in the Northwest and Southeast remain healthy in the face of climate change.”

“Conserving our nation’s fisheries and aquatic ecosystems will be a challenge as climate change continues,” said Salazar. “These collaborative research projects will provide the science and technology needed by the Interior Department and other natural resource managers to plan for coping with these challenges, especially in sensitive aquatic environments.”

Salazar noted that these projects are an early indication of the kind of science and management support that will be generated by the Interior Department’s regional climate science centers, which will be established in the Northwest and Southeast later this year. “Collaborative science targeted at managers needs is our agenda,” Salazar said.

The multi-year $500,000 joint USDA-DOI projects, which will be carried out by U.S. Geological Survey (USGS) and U.S. Forest Service (USFS) scientists, will make use of existing data, field studies and modeling to better understand the effects of climate change on aquatic ecosystems. Information from the project will help guide science-based land-use decisions by federal agencies and others engaged in long-term planning for climate adaptation.

In the Northwest, a region known for its abundant supply of cold and clean fresh water, the project’s goal is to identify how climate change will affect water temperature, quality and quantity, as well as the likely effects of increasing and more fluctuating water temperatures on coldwater-dependent fish such as trout and salmon.

Regional climate change will likely cause altered hydrology and water temperatures, vital components of water quality and healthy life cycles for species such as Pacific salmon, trout and chars, which depend on coldwater habitats. At the same time, little is known about existing and potential impacts of climate change for stream temperature in the Pacific Northwest. With a better understanding these factors – temperature and altered water flows – experts will be able to help guide land-use decisions by federal and state agencies planning for climate adaptation in the area.

In the Southeast, the project’s goal is to develop tools managers can use to minimize the effects of climate change on aquatic ecosystems and the coldwater-dependent species in them, as well as on related ecosystem service such as drinking water quality and wildlife-based recreation. The scientists will refine and combine climate and hydrologic models for the region that will help resource professionals assess how land-use and water-management decisions will affect coldwater fish species such as brook trout, and the transition from coldwater fisheries in the mountains to warm water fisheries in the lower-lying Piedmont area.

source: USDA