Although the high precipitation earlier this year and the resulting high flows from the dams have had some positive effects on the trout fisheries in the White and North Fork Rivers, these conditions have resulted in some of the lowest dissolved oxygen levels observed on these waters. When the dissolved oxygen levels began to drop below the state standard of 6.0 mg/l, the Corps of Engineers blocked open the turbine vents to allow more air to be entrained. This helped some, but as the season progressed the dissolved oxygen levels began to approach 4.0 mg/l. The Corps and Southwest Power instituted maximum loading restrictions on the turbine releases from the dams. This basically means that they are putting less water through the turbines to allow greater aeration. This helped to bring the dissolved oxygen levels back up and for that reason we continued to stock trout in all areas in an effort to maintain a satisfactory fishery. During this time we closely monitored the water quality situation and collected field samples to determine the extent to which sub-standard dissolved oxygen levels reached below the dams. However, the dissolved oxygen levels have continued to drop and despite the turbine venting and loading restrictions we are now seeing readings approach 3.0 mg/l. This is a threshold level where we could begin to see trout mortality and for that reason we have recommended to cease stocking in areas affected by low dissolved oxygen. Field samples taken earlier this week have shown that at the current flows the dissolved oxygen is not recovering to 6.0 mg/l until just above Rim Shoals on the White and until the bottom of the catch-and-release area on the North Fork. Therefore, we will cease stocking trout from the dam down to Cotter on the White and will only stock at Rose's Dock on the North Fork until conditions improve.
It should be noted that the fish that were scheduled for the affected areas will be held at the Jim Hinkle/Spring River Hatchery to be stocked in those areas when conditions improve. I realize the impact that these restrictions may have on many of you, however, this is a very unusual year. In fact, we have also instituted stocking restriction on the upper 6 miles of the Little Red for the first time ever.
I have attached a copy of the memos in which we recommended the stocking restrictions. Please let me know if you have any questions at all. Thanks. (M Tipton's note - I was unable to link to this memo)
