Big Lost fishery scrutinized
Trout Unlimited works toward balancing Western water use
By GREG STAHL
Express Staff Writer
Jim Gregory, Fisheries consultant
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Until the early-1980s, the upper Big Lost River contained one of the healthiest rainbow trout populations in Idaho, but, probably because of whirling disease, the fishery has spiraled downward the last 20 years.
With funding assistance from Sun Valley resident Ed Dumke, Trout Unlimited is trying to get to the bottom of the decline in a study spearheaded by the organization?s Idaho Falls-based Idaho Water Project.
?The Big Lost is a river we think is very important in this part of the world,? said Mike Clark, director of TU?s Western Water Project. ?Across the West, we?re seeing, as a result of 100 to 120 years of agricultural use, primarily, a lot of river reaches that are de-watered.?
The Big Lost River is fed by tributaries on the east slopes of the Boulder, Pioneer and White Knob mountains and the west slope of the Lost River Range. It meanders through cottonwood groves and through or near the rural cities of Mackay, Darlington and Moore, before disappearing in the porous soils of the Snake River Plain in the so-called ?sink? northeast of Arco.
In recent years, the riverbed near Arco has been dry, the entire river diverted for agricultural use upstream. The upper Big Lost is generally defined as the area above Mackay Reservoir, which is about five miles northwest of the city by the same name.
But the upper Big Lost River is not suffering as heavily as many rivers from a lack of water. In fact, fish populations in the heavily used river reaches below the reservoir are relatively healthy compared with the upper system.
For that reason, the study is focusing on reaches above Mackay Reservoir.
On Tuesday, Aug. 31, fisheries consultant Jim Gregory, presented an initial report on his research to curious local residents and members of Trout Unlimited during a meeting at the River Run Lodge in Ketchum. He called his work so far a ?desk assessment,? in which he has attempted to compile all of the available information on the river into one comprehensive study.
Whirling disease and an ongoing drought are probably the factors most responsible for fish declines in the upper Big Lost River, he said.
?It used to be such a good fishery that the Idaho Department of Fish and Game ignored it. It took care of itself,? Gregory said, explaining that data are difficult to find prior to the 1980s.
Whirling disease is a parastic infection that attacks juvenile trout and salmon, but it affects rainbow trout most severely. The water-borne parasite may not directly kill trout, but fish heavily infested can become deformed or exhibit the erratic tail-chasing behavior that gives the disease its name. Heavily infected young fish may eventually die.
To a lesser extent, fish populations in the upper Big Lost could be suffering from drought, because historic spawning corridors are cut off by irrigation diversions and a dry portion of the river channel called they Chilly Sinks, where the water soaks into the aquifer.
?There?s a possibility that fish used to go from the reservoir up to Copper Basin (west of the Pioneer Mountains),? Gregory said. ?This year, the Chilly Sinks were dry for about 10 months. That would make a pretty short window for fish to get through there in a drought year.?
Gregory offered a handful of suggestions that could help the upper Big Lost fishery recover. A fish ladder should be installed at an irrigation diversion above the Chilly Sinks to help facilitate fish migration into the Copper Basin area.
In order to deal with whirling disease, he said fish could be planted in areas where the parasite is not as prevalent. Also, species that are more resistant to the parasite could be stocked. The fine spotted cutthroat is a species the Idaho Department of Fish and Game has attempted to introduce, he said.
Although Gregory?s study did not point to agriculture as a primary culprit in the upper Big Lost River, TU representatives said one of the difficult challenges in the West is to balance sustainable agriculture with healthy rivers and streams.
?The task we face in thinking about trout in the West is largely about education,? Clark said. ?Eight of the fastest growing states in the country are in the interior West. If we want to preserve this region for our grand children, then we have some tough choices.?
Clark said 80 percent of the water in the West goes to irrigation.
?There is more than enough water in the West to meet the needs, but trout don?t have a place at the table,? he said.
The Western Water Project?s four main goals are to change state water laws to enable in-stream water rights, fight bad ideas, restore stream flows and create new incentives for landowners to change the way they?re doing business.
?We need to look at the whole process of how water law works in the West,? said Charles Gauvin, TU?s national director. ?When there?s a drought, our current laws combine natural disaster with an unnatural disaster.?
Gauvin said Western residents often pride themselves with being anglers and conservationists, but they often are blissfully unaware of how stressed the streams and fisheries are.
?It?s not going to be easy, but I can guarantee you it will be a lot easier than winning the war on terror,? he said.
