Twin Buttes Reservoir - 2003 Survey Report
Prepared by Mandy K. Scott and Brian E. Van Zee
Inland Fisheries Division
District 1-C, San Angelo, Texas
This is the authors' summary from a 24-page report. For a copy of the complete report, use the download link in the sidebar.
Twin Buttes Reservoir was surveyed in 2003 using electrofishing and trap nets, and in 2004 using gill nets. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.
Twin Buttes Reservoir is located on the South and Middle Concho rivers three miles southwest of San Angelo and is used for municipal water supply and irrigation. The reservoir consists of two main pools connected by an equalization channel. At the time of sampling the reservoir was 50 feet below conservation pool. Low water levels were maintained from 1995-1998 to facilitate repairs to the dam, and long-term drought has prevented the refilling of the reservoir. When full, access is good with 6 ramps and 100% of the shoreline available; however, currently none of the ramps are usable due to the low water level. At the time of sampling, the habitat was primarily nondescript, and rock and gravel shoreline.
- Prey species: Gizzard shad catch rates in 2003 (104.6/h) were similar to those in 2001 (93.0/h), but much lower than in 1998 (339/h). Index of vulnerability (IOV) rose from 75% in 1998 to 98% in 2003. With the higher IOV, prey availability is excellent. Bluegill CPUE remained low from 1998 (39/h) through 2001 (15/h) and 2003 (21/h). The CPUE of stock-size bluegill decreased over these years, resulting in higher availability to predators. The low water levels have likely limited growth and recruitment of most species, including prey.
- Catfishes: Blue catfish catch rates dropped from 1.0/NN and 1.3/NN in previous years to 0.1/NN in 2004. Channel catfish catch rates decreased from 1.6/NN in 2001 to 0.6/NN in 2004. There was an absence of small channel catfish in the sample, indicating that recruitment may be poor.
- White bass: White bass catch rates in 2004 (1.7/NN) were lower than in 1998 (5.2/NN), but slightly higher than in 1995 (0.4/NN). Relative weights (Wr) were low in all three years; most Wr values were less than 90. Growth and recruitment is likely being limited by low water levels.
- Largemouth bass: The largemouth bass population has been negatively affected by extremely low water levels. Catch rates have dropped from 50.7/h in 1998 to 11.0/h and 13.7/h in 2001 and 2003, respectively. The largest change occurred among stock-size fish, as the 8- to 12-inch group that had fairly high numbers in 1998 declined to very low numbers in 2001 and 2003. This resulted in higher PSD and RSD-14 statistics, but a lower overall catch rate.
- White crappie: The crappie population experienced a boost in 2003 from a strong age-0 year class. This resulted in an increase from 12.5/NN and 13.0/NN in 1998 in 2001, respectively, to 30.6/NN in 2003. Condition of crappie was good from 1998-2003, as indicated by relative weights between 90 and 110. PSD (57) and RSD-10 (38) were better than in previous years. Growth rates were also good, with crappie reaching 10 inches in 2 years. This population seems to be doing well despite the drought.
Because of continued extreme low water levels, no changes should be made to the current regulations on Twin Buttes Reservoir. After a significant rise in water level, supplemental sampling will be conducted to determine changes that should be made in stocking and sampling regimes. Supplemental stocking of channel catfish should take place to improve the catfish fishery for bank anglers at Twin Buttes.
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