SAN ANGELO – Biologists with the Texas Parks and Wildlife Department are monitoring increasing golden alga levels in reservoirs and rivers around San Angelo.

Golden alga is a single-celled organism that, under certain environmental conditions, can release toxins that affect fish, freshwater mussels and the juvenile stage of frogs and other amphibians. Golden alga only effects gill-breathing animals and poses no threat to humans or livestock.

Concern over increasing golden alga cell counts began when golden alga monitoring on Nov. 7 showed low toxicity in E.V. Spence Reservoir. Then in early December, anglers reported several large dead fish at the reservoir, which prompted additional samples. Water samples collected on Dec. 11 indicated moderate toxicity and a significant increase in golden alga cells in E.V Spence Reservoir.

“Although several large dead fish, including largemouth bass, catfish, and carp were reported by anglers, we have not yet seen a widespread fish kill at E.V. Spence,” said Lynn Wright, TPWD Fisheries Biologist in San Angelo. “At this time, it appears golden alga is having a limited impact on fish populations in the reservoir, but it is early in the season and further development is possible.”

Additionally, two reservoirs that have a history of golden alga problems, Colorado City and Moss Creek Reservoir, are also currently being affected. Colorado City Reservoir, which has been severely impacted annually by golden alga since 2001, showed high toxicity. Dead fish, including bullhead catfish and common carp, were also observed along the shoreline. Moss Creek had low toxicity on Nov. 7, but no dead fish were observed.

Golden alga was also found in the Concho River at Mullins Crossing at a moderate toxicity, but to date no dead fish have been observed in the Concho River. This section of the Concho River experienced a golden alga fish kill in the spring this year.

The good news is that locations where golden alga had previously been documented, including the Colorado River, O.H. Ivie Reservoir, Champion Creek and Brady Creek Reservoir were sampled and showed no toxicity in the samples.

The San Angelo fisheries management office, in coordination with other agencies, will continue to monitor golden alga throughout the winter and spring. Although large-scale treatment for golden alga is not feasible, TPWD biologists will evaluate the need for fish stocking after the golden alga blooms subside.

First discovered in Texas in 1985, golden alga (Prymnesium parvum) has since been responsible for fish kills in the Colorado, Canadian, Wichita, Red and Brazos river systems.

Additional information about golden alga and its effects on Texas reservoirs can be found online at http://tpwd.texas.gov/landwater/water/environconcerns/hab/ga/.