Friday, October 17, 2008

Low Dissolved Oxygen Stocking Requirements

From Jeff Williams

Hello All,

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.

Jeff

<> <Restriction Memo 10-2-08.doc>> http://webmail.aol.com/39155/aol/en-us/Mail/get-attachment.aspx?uid=1.23817789&folder=NewMail&partId=2&saveAs=Bull_Shoals_TW_Stocking_Restriction_Memo_10-6-08.doc


Jeffrey S. Williams
Trout Management Supervisor
Arkansas Game and Fish Commission
201 East 5th Street
Mountain Home, AR 72653
Phone: (870) 424-5924
Fax: (870) 425-6596
j_williams@agfc.state.ar.us

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