NORTHWEST TERRITORY : Oxygen levels, erosion under trout program review
Posted on Thursday, November 13, 2008
The problem of low dissolved
oxygen was among topics addressed
last week during an update of management plans for the state’s trout waters by Arkansas Game and Fish Commission trout-program leader Jeff Williams. Meeting with members of Trout Unlimited in Fayetteville, Williams said oxygen levels are below normal this year because of high nutrient content in waters flushed into the White River lakes during periodic flooding. “The deterioration of the nutrients further depleted oxygen levels along with the normal stratification of lakes caused by cooling water temperatures,” Williams explained. Trout biologists like to see dissolvedoxygen levels remain at or above 6. 0 milligrams per liter (mpl ), but they become especially concerned if levels drop to 4. 0 or lower. At that point, the trout become stressed, and some can die.
The dissolved-oxygen level in the Norfork tailwaters dipped below 6. 0 mpl in July, the earliest ever, and problems in the Bull Shoals tailwaters soon followed. Since then, levels have dropped to 4. 0 and below, Williams noted.
The Beaver tailwaters have been more fortunate, with levels dipping below 6. 0 mpl only once.
The Norfork tailwaters have suffered most, with levels of 2. 0 mpl having been recorded.
“We haven’t heard about a trout kill yet, but we’ve possibly lost a few,” Williams said.
The problem has led to a cessation of trout stocking in the Bull Shoals and Norfork tailwaters, but Williams said stockings could soon resume in the 24 miles of river below Bull Shoals Dam.
He described the situation on the Norfork as remaining critical.
From a historical perspective, Williams said that periodically low dissolved-oxygen levels in the tailwaters have been a known and lingering issue for 20-25 years.
When Bill Clinton was governor, he tried to get the commission, U. S. Army Corps of Engineers and the Southwest Power Administration together to come up with a solution. As recently as last month, Gov. Mike Beebe lent his support for a remedy.
Williams said there are measures that have proved successful at dams controlled by the Tennessee Valley Authority, but all are expensive. As usual, the question comes down to who pays.
“The Game and Fish [Commission ] position is that it’s a federal problem, and either the Corps or [Southwest Power Administration ] should pay,” Williams said.
If a solution can be worked out, it will be mostly applied first to the Norfork tailwaters.
In the meantime, Williams said the commission’s trout team will soon conduct a health-assessment survey of trout in the Bull Shoals and Norfork tailwaters to gauge the effects of low dissolved oxygen and prolonged strong-water releases.
He noted that dissolved-oxygen levels can vary from one part of the river to the other, such as between midstream and the banks and between pools and shoals. That might explain why the trout have been biting more vigorously in some places than others.
Regarding the Beaver tailwaters, Williams said the area soon will be receiving a lot of attention to assess the impact of the revamped trout-management plan that went into effect in January 2006.
The efforts will start later this month with an electro-fishing sample of the trout population, followed next month by a creel survey based on angler interviews.
Williams said the purpose of the latter is to determine if stockings may have been cut too much and if any adjustments to the slot limit of 13-16 inches may be needed.
Also in December, the trout team will conduct a growth and mortality study of Beaver tailwaters trout. In January, biologists will try to collect brown trout that have been specially marked so that their growth rate can be assessed. A first assessment in February 2007 indicated a growth rate of about 5. 5 inches per year, which is comparable to other tailwaters.
Also attending the meeting was Tim Burnley, habitat manager for the Beaver tailwaters, who gave an update on the impacts of flooding last spring.
He said the “J-vane” structures of the Parker Bend bank-fishing access withstood the opening of Beaver Dam’s flood gates.
Many other bank-stabilization structures along the tailwaters also survived largely intact, thanks in part to the high level of Table Rock Lake at the time of the flood releases.
Burnley said the main problem is bank erosion near the dam and other places along the tailwaters.
Plans call for a low-water survey to fully evaluate the full extent of erosion and any effects on in-stream habitat. The survey will employ the use of side-scanning sonar to look underwater.
To help fund the work to heal the erosion, Burnley said an application has been made to the Southeast Aquatic Resource Partnership for a grant from the National Fish Habitat Initiative Program.
“Our ranking looks good to be able to get a grant,” Burnley said.
A highlight of the meeting came when Sam’s Club manager Darrell Gabbard stepped forward to present the local chapter of Trout Unlimited with a $ 2, 000 check on behalf of the new Sam’s Club in Fayetteville.
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