Toxic Golden Algal Bloom in Texas


A toxic golden algal bloom on Lake Granbury that began the first week of January 2011 appears to be heading down the Brazos River toward Lake Whitney.

The Texas Parks and Wildlife Department (TPWD) Kills and Spills team and personnel with the Brazos River Authority have been conducting weekly fish kill investigations since early January. Water samples are taken monthly to assess golden alga toxicity and cell densities at various sites on Lake Granbury.

The toxic zone began on the upper end of the lake at Hunter Park and slowly spread down-lake over the course of the past two months. Currently, the active kill zone is concentrated at the dam, but dying fish were observed as far north as Rough Creek Park this week. As of the week of February 28, the estimated total number of dead fish due to this kill was 82,418. The vast majority, about 82 percent, of the affected fish are non-game species. Affected fish species include freshwater drum, channel catfish, flathead catfish, white crappie, white bass, largemouth bass, striped bass, various sunfish species, gar, gizzard shad, threadfin shad, and others.

On March 5 Somervell County Game Warden Joni Kuykendall was notified of a fish kill on the Brazos River below Lake Granbury. An investigation into that fish kill has begun. It is suspected that the toxic golden alga bloom is now in the Brazos River, affecting some 50 miles of river between Lake Granbury and Lake Whitney. Results are pending on a water sample taken to check for the presence and toxicity of golden alga in the river. An official estimate of dead fish in the river has not yet been completed; however, biologists believe the number of fish killed in the Brazos River over the past week may very well surpass the estimated number of fish killed in Lake Granbury over the past two months.

Lake Granbury is located on the Brazos River in the town of the same name southwest of Fort Worth. Fish kills due to golden alga were reported on the lake in 2004 and 2005.

First discovered in Texas in 1985, golden alga (Prymnesium parvum) was identified in a fish kill in the Pecos River and has since been responsible for fish kills in the Colorado, Canadian, Wichita, Brazos, Rio Grande, San Jacinto and Red river systems, affecting more than two dozen reservoirs and one coastal bay and killing at least 18 million fish. Golden alga has also impacted fish production at two TPWD fish hatcheries in the past.

Information about golden alga and the latest information on currently occurring blooms and fish kills may be found at //

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