J. B. Thomas Reservoir - 2003 Survey Report

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Prepared by Charles Munger and Jason Henegar
Inland Fisheries Division
District 1-A, Canyon, Texas

This is the authors' summary from a 26-page report. For a copy of the complete report, use the download link in the sidebar.

J. B. Thomas Reservoir was surveyed with electrofishing and trap nets in 2003 and gill nets in 2004. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.

Reservoir Description

J. B. Thomas Reservoir is a 7,820-acre impoundment (constructed in 1952) on the main stream of the Colorado River. Capacity during 2003 was approximately 6% of capacity or 2,065 acres. The reservoir has been at minimal capacity since 1995. The dam is located 16 miles southwest of Snyder and west of State Highway 208, in Scurry County, Texas. The reservoir is owned by the Colorado River Municipal Water District and provides water to four member cities. The reservoir has a drainage area of 3,950 square miles, however, it experiences frequent water level fluctuations. Since impoundment, the reservoir has never received sufficient runoff to fill to capacity. Angler and boat access is minimal. There are no handicap-specific facilities. Habitat consisted primarily of nondescript mud bank and flooded terrestrial vegetation.

Fish Community

• Prey species: Electrofishing catch rates for gizzard shad and bluegill were 314.0/h and 15.0/h, respectively. Catch rates were similar to the 1997 catch rates for both species. The IOV for gizzard shad was 95 and indicated sufficient availability to existing predators.
• Catfishes: The 2004 gill net catch rate for blue catfish was 17.6/NN and was much higher than the 1997 catch rate of 4.6/NN. Growth was poor with fish not reaching legal size until after age 8. The gill net catch rate of channel catfish for 2004 was 0.4/NN, down from 1997 (6.8/NN). The decline in channel catfish catch rate may be related to the increase in catch rate of blue catfish as has been seen in other Texas reservoirs. Age and growth was not determined due to poor sample size, however growth has historically been poor as fish did not reach legal size until age 9. Condition of the few fish sampled was over 100. The gill net catch rate of flathead catfish for 2004 was 1.8/NN, down from 1997 (2.6/NN). Condition was good for all sizes fish collected.
• White bass: The gill net catch rate for white bass in 2004 was 1.2/NN, similar to the 1997 catch rate of 1.0/NN.
• Largemouth bass: Electrofishing catch rate for largemouth bass was 20.0/h, the lowest documented since 1990 (Altena and Munger 1998). Mean relative weight for the population was average at 97 and growth was average with fish reaching legal size by age 4. Electrophoresis in 1997 indicated a 30% frequency of Florida largemouth bass alleles with none of the fish sampled having Florida largemouth bass genotype.
• White crappie: The trap net catch rate for white crappie was 29.5/NN in 2003, similar to the 1997 catch rate of 27.8/NN. Growth rates were poor with fish not reaching legal size until after age 4. Relative weights indicated fish ≥9 inches were in good condition while those <9 inches were in poor condition.

Management Strategies

Based on current information, the reservoir should continue to be managed with existing regulations.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-29 Statewide Freshwater Fisheries Monitoring and Management Program