Granger Reservoir - 2008 Survey Report
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Prepared by Greg A. Cummings and Stephan J. Magnelia
Inland Fisheries Division
District 2-C, San Marcos, Texas
This is the authors' summary from a 28-page report. For a copy of the complete report, use the download link in the sidebar.
Granger Reservoir was surveyed in 2008 using trap nets and boat electrofisher, and in 2009 using gill nets. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.
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.
Important sport fishes 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.
- Prey species: Threadfin shad continued to be present in the reservoir. Gizzard shad continued to be present and most remained available as prey to most sport fish. Bluegill were present.
- Catfishes: Blue catfish remained the dominant catfish species in the reservoir. Channel and flathead catfish were present in lower densities.
- White bass: White bass numbers increased in 2009. According to the 2005 creel survey this species was popular with bank anglers fishing in the upper reaches of the reservoir in the early spring. Most white bass reached legal length in two years.
- Largemouth bass: Electrofishing catch rate for largemouth bass increased in 2008. Increased catch rate for this species was due to strong year classes produced in 2006 and 2007, when water level was above conservation pool. Size distribution and body condition were good. Most largemouth bass reached legal length within one to two years. Supplemental stockings of the Florida sub-species of largemouth bass were made in the early 1990s. These stockings did not increase the genetic influence of the Florida subspecies.
- White crappie: White crappie were abundant and had good body condition. Most white crappie reached legal length within two years.
Based on current information, the reservoir should continue to be managed with existing regulations. According to the latest creel survey most of the directed fishing effort is for white crappie. Year class production and relative abundance fluctuate, so trap net surveys should be conducted annually to better monitor the population dynamics of this species. Blue catfish have established a self-sustaining population. Additional blue catfish stockings were not needed. Water hyacinth (Eichhornia crassipes) was found in 2004, but has not been documented on recent surveys.
Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-34 Statewide Freshwater Fisheries Monitoring and Management Program