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TPWD fisheries biologists unravel mysteries
By Jim Blassingame
Contributor
Published October 29, 2009
September means at least two unpleasant annual natural phenomena in East Texas: Ragweed is blooming and fish are dying at Lake Fairfield. Texas Parks and Wildlife Department (TPWD) Inland Fisheries management and Kills and Spills Team (KAST) biologists investigated a major fish kill on Fairfield Lake the second week of September.
Anglers fishing the lake the morning of Sept. 13 noticed the dead fish and notified the TPWD. Unlike previous kills, notification was received early enough that TPWD personnel were able to get to the scene while fish were still dying. This allowed them to collect fish that were stressed but not yet dead and take water samples in several areas of the kill.
Main locations of dead fish were along the shoreline of a cove immediately northwest of the dam to the spillway and in the cove south of the dam, but also extending up the shoreline to mid-reservoir. The fish appeared to have died no earlier than Saturday, Sept. 12.
TPWD personnel returned to the lake to collect water samples and conduct a thorough investigation and enumeration of the kill. Water quality field data were measured both in and out of the area where dead fish were observed. Dead fish were distributed along approximately 10 miles of shoreline. A series of detailed counts were conducted along approximately 0.75 miles of that shoreline to allow estimation of the total kill.
Water quality datasondes (electronic data gathering devices) were deployed in the northwest and south coves where the main kills occurred. These datasondes were able to collect temperature and oxygen concentration every 30 minutes for the following 14 days.
Water quality field data collected on Sunday the 13th indicated extensive areas of lower than normal oxygen and abundant phytoplankton (chlorophyll a) in the areas where the fish kill occurred. Using information on oxygen concentration from the datasondes, water quality data collected the day of the kill, and information on sunlight level from a local weather site, TPWD biologists began to piece together a theory on the cause or causes of the kill.
Normally photosynthesis (oxygen production) by phytoplankton during daylight hours increases oxygen concentration enough to compensate for respiration (oxygen use) by those same phytoplankton as well as bacterial decomposition at night. However, during periods of cloudy weather sunlight (measured as solar radiation) is reduced; oxygen consumption remains high but oxygen production is greatly reduced. When cloudy weather lasts for several days and oxygen concentration falls below the minimum level to support aquatic life, fish begin to die.
A good rule of thumb is at oxygen concentrations below 5 milligrams per liter (5 mg/L) many species become stressed, and at concentrations below 3 mg/L most species can die from oxygen deprivation. Although oxygen levels may stay above the minimum level during the day, it only takes a few minutes below the minimum at night to be fatal to fish.
Initial estimates from the 2009 TPWD fish kill investigation indicated that nearly 1 million fish died compared to an estimated 7,345 that died in September 2008 and an additional 114,223 that October. However, the species distribution in the current kill was considerably different than in September 2008. In 2009, 96% of the kill (an estimated 875,793 fish) were threadfin and gizzard shad and 3.3 percent (an estimated 30,168 fish) were sunfish species; the remaining fewer than one percent were bullhead minnow, inland silverside, channel catfish, flathead catfish, yellow bullhead, largemouth bass, blue tilapia, and red drum. In the 2008 kill, 51% were large red drum with an average length of 32 inches.
Water samples and tissue samples from live but stressed fish collected during the day of the kill have not shown the presence of any toxicant that could be responsible for the kill.
TPWD has stocked more than 5.3 million red drum in Lake Fairfield since 1984, and despite the estimated 3,750 red drum lost in the 2008 kill and the far lesser number lost in the present kill, anglers fishing the lake report excellent success for this popular fishery.
Fishing reports
Pat Mayse Lake: As you already know, this lake is full and with the weather we have been having, there are not a lot of folks out on the lake. The only tip that I have - and it makes no difference what kind of fisherman you are, just “power fish.”
With all the water, fish of all kinds will be scattered, so keep a bait in the water and fish different depths (zig-zag) and cover as much water as you possibly can. I recommend square-bill cranks, lipless cranks, spinnerbaits and swim jigs. You can use the swim jig when you get in close and fish under and in the flooded bushes or behind cattails.
Lake Fork: The lake levels are very high here also, but the Sabine River Authority is pulling water from the lake. About the same report here, not a lot of folks are out on the water. The forecast looks pretty good for the weekend, and here I would recommend working with the same baits and I would stay in 8 to 18 feet of water with wood and grass for cover.
Hugo: I have not been over behind the dam here, but I have had several good reports on catfish. I would be willing to bet my best spinnerbait that you can also catch some crappie as well.
This weekend, I would recommend hitting smaller lakes without gates, then you will not be faced with the falling water because this makes for a slow bite. Also, I ran across an old Irish blessing and I want to pass it along to you:
“May the holes in your dip-net be no bigger than the fish in it.”
Be safe, fish smart and I’ll see you on the lake!
Jim Blassingame is a Paris resident and an avid angler.
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