J. B. Thomas Reservoir - 2023 Survey Report

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

This is the authors' summary from a 26-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, 2021, and 2023 using electrofishing, 2019 and 2023 trap netting, and in 2022 and 2024 using gill netting. Historical data are presented with the 2019-2024 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 31.4 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 with standing timber in the upper one third of the reservoir.

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. Largemouth Bass were stocked in 2022. Florida Largemouth Bass were stocked in 2015, 2016, and 2018.

Fish Community

• Prey species:  Gizzard Shad and Bluegill populations in the reservoir are adequate to support the existing predator population. Electrofishing catch rate for Gizzard Shad for 2023 was very high with ninety-eight percent of sampled shad available as prey to most sportfish. Electrofishing catch rate of Bluegills for 2023 was lower than previous surveys, but all Bluegills sampled were 5-inches and smaller making them available as prey.
• Catfishes:  Blue Catfish catch rates appear fairly stable with a slight increase since 2018. Juvenile Blue Catfish in the 2022 and 2024 surveys indicate that natural reproduction is occurring in the reservoir. The Channel Catfish catch rates have shown a steady decline since 2018; both juvenile fish as well as fish larger than 15-inches were sampled in the last three surveys. Flathead Catfish were present in the reservoir.
• Largemouth Bass:  Periods of high turbidity in the reservoir are believed to affect the electrofishing results from year-to-year. The catch rate for 2023 was similar to the 2019 survey and slightly higher than the 2021 survey. The population appears to be shifted towards larger individuals with few juvenile fish observed during sampling surveys. The majority of fish sampled were of legal harvestable size with individuals as large as 21 inches observed. Growth appeared good with fish reaching legal size in an average of 2.2 years.
• White Crappie: White Crappie were abundant. The population appears to be balanced with several legal sized fish being observed during the 2023 survey. A large number of juvenile fish present in the 2023 survey indicates the possibility of numerous legal sized fish during the next year.

Management Strategies

Conduct surveys with electrofishing in 2025 and 2027, trap nets in 2027, and gill nets in 2026 and 2028. Conduct age and growth analysis of Largemouth Bass in 2025 and 2027 and genetic analysis of Largemouth Bass in 2027. Continue educating the public about the dangers of invasive species. Habitat and vegetation surveys will be conducted in 2027.

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