Dissolved Oxygen Profile:
We often hear our Hot Springs area anglers commenting on the depth of the summer thermocline. Most anglers know of the thermocline which becomes well established during the late summer months. Anglers are also aware black basses and walleyes will congregate just above the thermocline seeking cooler oxygenated water as the surface temperatures have become too warm for them.
Dissolved oxygen profiles were conducted on Lake Ouachita late July 2015 & on DeGray Lake early August 2016. Fisheries District 8 biologists Brett Hobbs and Sean Lusk wanted to provide this information to our area anglers to better help them understand positioning of striped bass at Lake Ouachita and hybrid striped bass at DeGray Lake.
On both Lake Ouachita and DeGray Lake, the water temperature just above the top of the thermocline will be close to 80°F. Largemouth bass, spotted bass, and walleye are more comfortable at 80°F versus the water approaching 90°F at the surface.
The thermocline is a thin but distinct layer in a large body of water in which the temperature drops rapidly with increasing depth. This is represented on the attached charts by the horizontal grouping of data points on the dissolved oxygen (DO) chart. The typical late summer thermocline will vary between 19 to 25 feet deep on both lakes. This rapid drop in temperature is also accompanied by a distinct drop in dissolved oxygen levels.
The available dissolved oxygen level just below the thermocline becomes uninhabitable by most fishes down to a certain depth until the dissolved oxygen levels “rebound” to a level considered inhabitable by certain sport fishes. On DeGray Lake this rebound in oxygen occurs at a depth of about 40 to 45 feet and this is where anglers report hybrid stripers holding during this period. On Lake Ouachita this occurs also but the oxygen does not reach a level preferred by striped bass (about 2.5 ppm) until you get down to 50 or 55 feet.
If you are a live bait angler pursuing hybrids or stripers on either of these fisheries you may have lowered your baits below the thermocline and wondered why they died. It could be one of two reasons: the oxygen level was too low or the colder water temperature thermally shocked the bait and they succumbed to the extreme temperature change.
Keep in mind the oxygenated thermal refuge area decreases toward the dam on each of these reservoirs as summer progresses. This is typically caused by regular hydropower water removal from both lakes through the turbines at the dam.
Hope this information helps make you a better fisherman……Happy Fishing.
LOSBA has been helping AGFC stock striper fingerlings in Lake Ouachita. With the help of striper guides Mike Perry (Lil gunn), Randy Nelson, and John T. Hall, we were able to put around 87,000 fingerlings in the lake with more to come. Next we will help collect striper skeletons so AGFC can perform aging studies.
May 22, 2016
LOSBA had its first official meeting and our guests were Brett Hobbs and Sean Lusk from Arkansas Game and Fish. Brett is a biologist in charge of the striped bass project at the Andrew H. Hulsey State Hatchery in Hot Springs, AR and Sean is his new assistant and recent graduate of Auburn University.
A number of local striper guides were in attendance also, and all were able to ask several questions that Brett and Sean were gracious enough to answer. We learned of some of the exciting things the AGFC are doing, one of which is a new method for aging the fish.
Other items discussed was the stocking of the lake with striper, how to get more protein in the lake to promote growth in the fish, and a possible study of how many anglers are fishing Lake Ouachita for striped bass.
LOSBA has agreed to work with Brett and Sean on trying to collect striper (skeletons) for studying, attempting to determine how much activity is on the lake during the seasons, along with an estimate of the amount of striper being caught each year by anglers. All of this is important for the work that Brett, Sean and the rest of AGFC do for all the lakes they service.
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