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Granger Reservoir - 2004 Survey Report

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Prepared by C. Craig Bonds and Stephan J. Magnelia
Inland Fisheries Division
District 2-C, San Marcos, Texas

This is the authors' summary from a 32-page report. For a copy of the complete report, use the download link in the sidebar.

Granger Reservoir was surveyed in 2004 using trap nets and boat electrofisher, and in 2005 using gill nets. Structural habitat, aquatic vegetation, and angler access surveys were conducted in 2004. An angler creel survey was conducted in spring (March – May) 2005. This report summarizes the results of these surveys and contains a fisheries management plan for the reservoir based on those findings.

Reservoir Description

Granger Reservoir is a 4,009-acre impoundment of the San Gabriel River in Williamson County. The reservoir is located approximately 40 miles northeast of Austin, Texas, within the Brazos River drainage. It was constructed in 1980 by the U. S. Army Corps of Engineers (USACOE) for purposes of flood control and water conservation. Granger Reservoir has a drainage area of approximately 709 square miles and a shoreline length of about 40 miles.

A significant portion of the reservoir is bordered by the Granger Wildlife Management Area. The USACOE controls four parks. Each park provided camping and a boat ramp. Bank access was good within the park boundaries and Wilson Fox park on the south shore contained a fishing pier accessible to physically challenged persons.

Aquatic Vegetation

Turbid water limited the presence of submerged aquatic plants. Water clarity, expressed as secchi depth, was typically less than 1 foot, but clarity generally increased toward the dam. No aquatic plants were observed growing in Granger Reservoir prior to 2003. In 2003, hydrilla was discovered within the Wilson Fox Park boat ramp cove. The USACOE conducted a herbicide treatment in 2003, and no hydrilla was observed in 2004. However, the 2004 aquatic vegetation survey documented several isolated patches of the exotic, floating aquatic plant water hyacinth in the upper San Gabriel arm of the reservoir. Total coverage of these colonies was 0.3 acres. Following heavy rains and high reservoir inflows, no hyacinth plants were observed during survey trips in Spring 2005.

Spring 2005 Creel Survey

Pole and line anglers expended an estimated 36,542 (RSE = 13.2) hours (9.1 hours/acre) of fishing during daylight hours from March through May 2005. Total angler trip expenditures were estimated at $172,222 (RSE = 41.4). Most (61.8%) anglers traveled less than 30 miles, and 92.7% traveled less than 50 miles to fish this reservoir. White crappie was the most sought after species (61.5% directed angler effort), followed by catfishes (16.8%), white bass (5.1%), and largemouth bass (2.5%).

Fish Community

Management Strategies

Based on current information, the reservoir should continue to be managed with existing regulations. White crappie anglers accounted for the majority of fishing effort during spring months. Anecdotal angler reports attest to the popularity of this species throughout the year. Year class production and relative abundance have fluctuated in past years. Trap net surveys
should be conducted annually to better monitor the population dynamics of this species. Bank anglers were equally successful at catching white crappie during spring months compared with boat anglers. The shallow/near-shore movements of spawning white crappie allowed these fish to be accessible to bank anglers during this time. Public bank access was good inside park boundaries and on a fishing pier. Many anglers without access to a boat may not be aware of bank fishing opportunities on this reservoir. Bank fishing opportunities should be communicated to anglers through appropriate media outlets.

The blue catfish population has established a self-sustaining population. Additional blue catfish stockings are not warranted. The channel catfish population continued to decline following the stocking of blue catfish. Anglers may be able to improve success by altering angling techniques to target blue catfish. This strategy should be communicated to local anglers through appropriate media outlets.

An herbicide treatment eliminated hydrilla from the Wilson Fox boat ramp cove in 2003. High reservoir inflows eliminated newly discovered (Summer 2004) water-hyacinth plants from the upper San Gabriel arm of the reservoir by Spring 2005. These exotic aquatic plants have the potential to rapidly spread and inhibit bank fishing access. Annual surveys should be conducted to monitor for the presence of these two aquatic plants. If hydrilla or water hyacinth plants return, treatment options should be coordinated with the USACOE.

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



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