TPWD fisheries biologists solve mystery of dying fish

FAIRFIELD, Texas-- 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 September 13th noticed the dead fish and notified the TPWD 24-hour Communication Center at

512) 389-4848. 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 midreservoir. The fish appeared to have died no earlier than Saturday, September 12th.

TPWD personnel returned to the lake on Monday the 14th and Tuesday the 15th 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.

By combining oxygen data from the datasondes with solar radiation data from the weather station, TPWD biologists now had the critical information needed to understand the complex dynamics of the repeated kills at Lake Fairfield.

In September, water temperature and bacterial activity are still high but day length has been getting shorter incrementally since the summer solstice on June 21 (the date in the Northern Hemisphere when daylight hours are longest relative to dark). Extremely high phytoplankton levels due to high nutrient levels produce sufficient oxygen during sunny days to compensate for lack of production at night; however, when early fall cool fronts and cloudy weather limit solar radiation, oxygen levels drop rapidly and fish may die.

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% (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. Anglers spent over 9,000 angler hours seeking red drum at Lake Fairfield from September 1, 2008 through May 31, 2009, accounting for over 47% of the directed effort; angling continued during and after both fish kills.

The TPWD Kills and Spills Team is a group of biologists who respond to pollution reports or natural incidents that threaten state fish or wildlife resources. If you see dead or dying fish or wildlife or pollution threatening fish and wildlife, please contact the 24-hour Communication Center at (512) 389-4848, or contact your local game warden. Additional information about KAST is available at http://www.tpwd. state.tx.us/texaswater/kast/ pages/homepage.html.

Questions about the Fairfield Lake fishery should be directed to District Biologist Richard Ott at (903)-566- 2161, richard.ott@tpwd.state. tx.us.