Granger Reservoir - 2012 Survey Report

Prepared by Muhktar Farooqi and Marcos J. De Jesus
Inland Fisheries Division
District 2-C, San Marcos, Texas

This is the authors' summary from a 34-page report. For a copy of the complete report, use the download link in the sidebar.

Fish populations in Granger Reservoir were surveyed in 2012 using electrofishing and trap netting and in 2013 using gill netting. Historical data are presented with the 2012-2013 data for comparison. This report summarizes results of the 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 (USACE) 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. High turbidity and fluctuating water levels have deterred the establishment of aquatic vegetation. Reservoir bank slope is relatively flat and small changes in water level (1-2 feet) can have a large impact on the abundance of shoreline habitat and river/reservoir connectivity.

Management History

Important sport fish include White Crappie, White Bass, Largemouth Bass, and catfish. A creel survey conducted in the spring of 2005 showed 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%; Bonds and Magnelia 2005). Blue Catfish were stocked in 1995 and 1996 to provide additional angling opportunities and utilize an abundant shad population. No additional stocking has been conducted since 1996.

Fish Community

• Prey species: Threadfin Shad and Gizzard Shad were the predominant prey species available. The index of vulnerability for Gizzard Shad was 99 indicating that most remained available as prey to most sport fish.
• Catfishes: Total catch per unit effort for blue and Channel Catfish species was relatively low. Flathead Catfish were not recorded.
• White bass: Total catch per unit effort and catch rate of harvestable size fish had decreased since the previous survey, but fish up to 15 inches in length were present. On average, White Bass reached harvestable size (10 inches) between age 1 and 2.
• Largemouth bass: Electrofishing catch rate for Largemouth Bass had significantly decreased since the 2008 survey. The only harvestable size fish caught was 15 inches in length.
• White crappie: White Crappie were abundant and had good body condition. On average, White Crappie reached harvestable size (10 inches) between age 1 and 2.

Management Strategies

Based on current information, the reservoir should continue to be managed with existing regulations. White Crappie is by far the most sought-after species at this reservoir; therefore trap net surveys should be conducted annually to better monitor the population dynamics of this species.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-221-M-3 Inland Fisheries Division Monitoring and Management Program