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Golden Alga Impacts Two Central Texas Reservoirs
AUSTIN — Golden alga (Prymnesium parvum) has once again impacted two very important reservoirs and fisheries on the Brazos River system. Texas Parks and Wildlife Department biologists have been monitoring golden alga blooms and resulting fish kills on both Possum Kingdom Reservoir and Lake Whitney.
According to Melissa Tidmore, a biologist on TPWD’s Inland Fisheries Kills and Splills Team, golden alga is a naturally-occurring, microscopic alga that, under certain environmental conditions, can cause massive fish mortality by releasing a toxin that inhibits fishes’ ability to breathe. Golden alga was first identified in Texas in the mid-80s in the Pecos River. Since then, golden alga blooms have affected numerous public water bodies in Texas including 33 major reservoirs, numerous community fishing lakes, and two state fish hatcheries.
The effects of toxic golden alga blooms can be devastating to fisheries. Since 2001, golden alga blooms have caused more than 130 major fish kills and resulted in the loss of more than 34 million fish valued at more than $14 million.
TPWD continues to work closely with golden alga experts and researchers from around the world, as well as seven different Texas universities, and to date has focused more than $4 million toward golden alga research.
"Unfortunately, while we have learned a lot about golden algae and have identified ways of controlling it in our hatcheries and in small ponds there still is no viable method for controlling it in large reservoirs," said Brian Van Zee, TPWD Inland Fisheries Division Regional Director in Waco. "The department will continue to make it a priority to manage and enhance the fisheries at both of these reservoirs as well as others impacted by golden alga. Once these events subside, our fisheries staff will assess the damages to the fish populations and implement efforts to restock and manage these fisheries."
This winter, golden alga cell densities on Possum Kingdom began increasing and by early March anglers started to report dead and dying fish. The toxic bloom started on the upper end of the reservoir near Rock Creek Camp. During the initial investigations, the bloom seemed to be "patchy," with only small numbers of dead fish being found at various locations.
However, in mid-March water samples taken throughout the reservoir showed an increase in both cell densities and toxicity. Additional surveys were conducted in April and by mid-April dead and dying fish were observed from the South D&D boat ramp to the dam, with a large concentration of dead fish in Neely Slough. To date, the estimated fish killed by the bloom on Possum Kingdom is about 50,000; the majority of which were gizzard shad. Other commonly observed species included channel catfish, white bass, largemouth bass, striped bass, sunfish and freshwater drum.
On Lake Whitney the toxic bloom began in mid-March on the upper end of the lake near Juniper Cove. At the onset of the bloom, dead and dying fish, mostly threadfin shad, were observed on the east side of the lake from the Katy Bridge to Cedar Creek. However, during the most recent investigation, dead fish were concentrated at the lower end of the lake near Lofers Bend, Soldiers Bluff, and Little Rocky Creek. To date, the total estimated number of dead fish on Lake Whitney is upward of 68,000. The majority of fish affected were gizzard shad, threadfin shad, and freshwater drum; however, other species, including sunfish, striped bass, white bass, channel catfish and crappie were also observed.
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