Calaveras Reservoir - 2003 Survey Report

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Prepared by John A. Dennis
Inland Fisheries Division
District 1-D, San Antonio, Texas

This is the authors' summary from a 21-page report. For a copy of the complete report, use the download link in the sidebar.

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

Reservoir Description

Calaveras Reservoir is a 3,450-acre impoundment located on Chupaderas and Calaveras Creeks in the San Antonio River Basin. It is located 17 miles from San Antonio and was built in 1969 by the City Public Service Board of San Antonio (CPSB). The reservoir is used for power plant cooling and recreational purposes. A near-constant level is maintained by pumping from the San Antonio River during periods of low rainfall and runoff. Access and recreational facilities, built and maintained by the San Antonio River Authority (SARA), were found to be adequate. In 2003, two special projects were initiated at Calaveras. The first was a joint project with Texas Parks and Wildlife, City Public Service, SARA, and PBS&J Associates to reintroduce aquatic vegetation. The second was a project to reintroduce native largemouth bass.

Fish Community

• Prey species: Electrofishing catch rate of gizzard shad was 40.0/h in 2003, a decline from 89.0/h in 2002, but much greater than the 6.0/h in 2000. The Index of Vulnerability (IOV) of gizzard shad was 75, which indicated good availability to predators. Electrofishing catch rate of threadfin shad was 115.0/h. Electrofishing catch rate of bluegill was 501.0/h, an increase from the 346.0/h in 2002 and 80.0/h in 2000. The majority of bluegill collected in 2002 were less than 5-inches long, indicating a good availability to predators. Electrofishing catch rate of all other prey species combined was 346.0/h.
• Blue catfish: Seven blue catfish (1.4/NN) were collected in gill nets indicating a continued presence in the reservoir.
• Channel catfish: Gill net catch rates have increased over the last three surveys (7.6/NN in 2002, 12.6/NN in 2003, and 23.4/NN in 2004) as have Proportional Stock Densities (PSD’s) (14 in 2002, 27 in 2003, and 45 in 2004). Relative Weight (Wr) values in 2004 were all above 90.
• Palmetto bass: Gill net catch rates of palmetto bass have shown a steady decline over the last 3 surveys (16.0/NN in 2002, 5.2 in 2003, and 2.2 in 2004). Proportional Stock Density (PSD) and Relative Stock Density of Preferred-sized fish (RSD-P) were 100. This is likely a reflection of our stocking history (in 2002, only ½ of the number of hybrid striped bass requested for stocking were actually stocked, and none were stocked in 2003).
• Largemouth bass: Electrofishing catch rate of largemouth bass was 29.0/h in 2003 which was an increase over the 9.0/h collected in 2002, and 0.0/h in 2000. PSD was 29 which is lower than the previous survey (44 in 2002). RSD-P has declined from 11 in 2002 to 7 in 2003. Relative weights were above 100. Growth rates of largemouth bass were good with fish reaching 14-inches by age 1. Electrophoresis indicated a 66.7% frequency of Florida largemouth bass alleles with 55.2% of the population having Florida largemouth bass genotypes.
• White crappie: One 7-inch white crappie was collected in trap nets in 2002 following a management stocking of 244 sub adults in 2001. Another management stocking of 850 sub adults was conducted in 2004.
• Red Drum: Gill net catch rates of red drum have increased steadily from 0.6/NN in 2002 to 1.4/NN in 2003 to 2.4/NN in 2004. PSD was above 90 for all 3 surveys and RSD-P was 73 in 2004.

Management Strategies

• Continue to work with the City Public Service, SARA, and PBS&J to reintroduce and evaluate planting success of native aquatic vegetation.
• Continue to monitor the results of the management stockings of sub adult white crappie.
• Continue annual stockings of palmetto bass and red drum.
• Continue to assist Heart of the Hills with their native largemouth stocking evaluation.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-28 Statewide Freshwater Fisheries Monitoring and Management Program