Colorado City Reservoir - 2008 Survey Report

Prepared by Mukhtar Farooqi and Mandy K. Scott
Inland Fisheries Division
District 1-C, San Angelo, Texas

This is the authors' summary from a 15-page report. For a copy of the complete report, use the download link in the sidebar.

Fish populations in Colorado City Reservoir were surveyed in 2008 using electrofishing and trap nets, and in 2009 using gill nets. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.

Reservoir Description

Colorado City Reservoir is a 1,618-acre reservoir located on Morgan Creek, a tributary of the Colorado River, west of Colorado City in Mitchell County, Texas. It is a power-plant reservoir with habitat consisting primarily of flooded terrestrial vegetation, native emergent vegetation, boulders and boat docks. The water level has remained within 15 feet of conservation pool for the last 21 years largely due to pumping water from Champion Creek and Moss Creek reservoirs to maintain water levels at a sufficient elevation for power generation. The Morgan Creek Power Plant is only operated periodically and is scheduled to be closed. Colorado City reservoir has been severely impacted by toxic golden alga (Prymnesium parvum) blooms every year since 2001. Fish kills have been routinely documented. Boat and shoreline access were good.

Management History

Historically, important sport fish included largemouth bass, white bass, channel catfish and blue catfish. Red drum were once an important species in this reservoir, but the loss of the thermal refuge that used to exist (due to warm water discharge from the power station) meant that these fish would not be able to survive through natural winter temperature regimes. Colorado City Reservoir has been impacted by toxic golden alga blooms, and a concerted effort was made to restock the reservoir when water quality was suitable. Florida largemouth bass (603,683) and bluegill (863,965) were stocked during 2004-2008 and channel catfish (1,054,326) during 2003-2008. In the presence of intermittent long-term toxic conditions these stocking efforts have largely failed to establish populations capable of supporting viable fisheries. As a result, all fish stocking in this reservoir has been suspended pending sustained improvements in water quality.

Fish Community

• Prey species: Electrofishing catch of gizzard shad was fair and a high proportion of fish (99%) was available as prey. Electrofishing catch of bluegill was extremely poor.
• Catfishes: No channel catfish, blue catfish or flathead catfish were collected by gill nets in 2009. No channel catfish or blue catfish have been caught since 2000 and no flathead catfish have been caught since 2001.
• Temperate basses: No white bass were collected during sampling in 2009. Zero have been collected in gill net surveys since 2000.
• Largemouth bass: Abundance was fair, but size structure was poor. No largemouth bass ≥11 inches in length were collected in 2008.
• Crappie: One 4-inch white crappie was collected by trap netting in 2008. This is the first one to be recorded since 2000.

Management Strategies

Based on current data, Colorado City Reservoir should continue to be managed with existing regulations. Future stockings would be contingent on sustained improvements in water quality as determined by monitoring cell density and toxicity levels of golden algae. A mandatory standard survey is scheduled to be carried out in 2012-2013 with trap nets, gill nets, and electrofishing gear to determine the status of fish populations. Additional sampling is scheduled for 2010-2011 with electrofishing gear and gill nets to monitor the fish populations.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-34 Statewide Freshwater Fisheries Monitoring and Management Program