J. B. Thomas Reservoir - 2019 Survey Report

Prepared by John Clayton and Caleb Huber
Inland Fisheries Division – Amarillo District

This is the authors' summary from a 23-page report. For a copy of the complete report, use the download link in the sidebar.

Fish populations in J.B. Thomas Reservoir were surveyed in 2019 using electrofishing and trap netting and in 2018 using gill netting.  Historical data are presented with the 2018-2019 data for comparison.  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 Colorado River. The dam is located 16 miles southwest of Snyder and west of State Highway 208, in Scurry County, Texas.  The reservoir is operated by the Colorado River Municipal Water District (CRMWD) and provides water to three member cities. The reservoir has a drainage area of 3,950 square miles; however, it experiences frequent water level fluctuations, and the reservoir was last full in 1962. The reservoir declined steadily from approximately 3,917 acres in 2005 to 320 acres in 2012 due to drought and municipal water pumping. In 2014 and 2015 the watershed experienced large rain events, and the reservoir increased in size to 6,233 acres and was 3 feet below Conservation Pool elevation (approximate 46-foot rise).  Currently the reservoir is 29.7 feet below Conservation Pool. Angler access is good as most of the shoreline is accessible, but only one of four boat ramps is open and usable.  At the time of sampling, habitat consisted primarily of sand/silt and rocky shore covered with standing timber.

Management History

Important sport fish include Largemouth Bass, White Crappie, and catfishes. Florida Largemouth Bass were introduced in 1980.  Due to extended drought followed by a large rise in lake level, Blue and Channel Catfish were stocked in 2015. Bluegill were stocked in 2016. Florida Largemouth Bass were stocked in 2015, 2016, and 2018.  The sport fish populations have only been managed with statewide regulations.

Fish Community

• Prey species:  Gizzard Shad and Bluegill populations in the reservoir are adequate to support the existing predator population. Ninety-nine percent of sampled shad were available as prey to most sport fish.  Electrofishing catch of Bluegills for 2019 was higher than 2017 but lower than 2018. All Bluegill sampled were 5-inches in length and smaller.
• Catfishes:  Blue Catfish catch rates appear stable since 2016 with a slight shift towards larger individuals.  Juvenile Blue Catfish in the 2018 survey also indicate that natural reproduction is occurring in the reservoir. The Channel Catfish population also appears to be recovering from the extended period of drought observed through 2014; both juvenile fish as well as legal sized fish were sampled.  Flathead Catfish are present in the reservoir.
• Largemouth Bass:  Periods of high turbidity in the reservoir are believed to affect the electrofishing results from year-to-year.  Although the catch rate for 2019 was lower than 2018, the population appears to be well balanced. The majority of fish sampled were of legal harvestable size with individuals as large as 22 inches observed
• White Crappie:  White Crappie abundance appears to be increasing; however, most fish observed in the 2019 survey were below 10 inches.

Management Strategies

Conduct surveys with electrofishing in 2021 and 2023, trap nets in 2023, and gill nets in 2022 and 2024. Conduct genetic analysis and age and growth analysis of Largemouth Bass in 2023. Continue educating the public about the dangers of invasive species. Habitat and vegetation surveys will be conducted in 2023.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-221-M-6 Inland Fisheries Division Monitoring and Management Program