Granbury Reservoir - 2005 Survey Report

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Prepared by Michael S. Baird and John Tibbs
Inland Fisheries Division
District 2-B, Waco, Texas

This is the authors' summary from a 30-page report. For a copy of the complete report, use the download link in the sidebar.

Fish populations in Granbury Reservoir were surveyed in 2005 using electrofishing and trap nets and in 2006 using gill nets. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.

Reservoir Description

Granbury Reservoir is an 8,700-acre impoundment located within the Brazos River system, Hood County, Texas. Constant water level is maintained by an open spillway and retention time has been estimated at 260 days. Granbury Reservoir has been hampered by golden alga since 2001. Habitat features mainly consisted of boat docks, extensive bulk heading, standing timber, and dead trees and stumps.

Management History

Important sport fish include largemouth bass and striped bass. Both have been affected by annual, toxic golden alga blooms since 2001. Prior to this, largemouth bass were being regulated with a more restrictive 16-inch minimum length limit, five fish daily bag, which is still in place today. Stripers have been regulated with statewide regulations, and although more restrictive limits were considered in 2002, the desire to maintain consistent regulations for user groups on Granbury and Whitney Reservoirs out-weighed expected benefits at the time. Other species of fish have withstood significant mortalities over the past five years; fortunately the prey base has rebounded nicely year after year. Recent efforts to mitigate the loss of sport fish due to golden alga have included annual striped bass stockings since 2001 and Florida largemouth bass stockings in 2003 and 2004.

Fish Community

• Prey species: Threadfin shad are still present in the reservoir in low density. Electrofishing catch rates for gizzard shad have returned to pre-golden alga levels, with similar numbers of the species available as prey to most sport fish. Electrofishing catch rates of bluegill and other sunfish species was lower than normal, with very few individuals reaching memorable sizes.
• Catfishes: The channel catfish population has slowly shifted to one with larger, healthy individuals and low recruitment. Flathead and blue catfish, although present in the reservoir, make-up a small portion of the fishery.
• Temperate basses: White bass catch rates have historically fluctuated in Granbury Reservoir and current gill netting catch rates are slightly above average. Individuals up to 15-inches are common. Striped bass are stocked on an annual basis and are present in the reservoir at a much-reduced density.
• Largemouth bass: Largemouth bass electrofishing catch rates were well below pre-golden alga levels yet size structure was good. There were good numbers of preferred and memorable sized fish.
• White crappie: White crappie are present in the reservoir. Although catch rates are low compared to pre-golden alga trap net surveys, individual relative weights are excellent.

Management Strategies

• Continue annual stocking of striped bass at 10-fish/acre and Florida largemouth bass at 25-fish/acre in 2007 to mitigate losses due to golden alga.
• Conduct electrofishing and trap net surveys in 2007, a gill net survey in 2008, and standard monitoring with trap nets, gill nets, and electrofishing in 2009-2010.
• Conduct aquatic vegetation survey as required and an updated habitat survey prior to the next survey report.
• Continue assisting with golden alga research as needed.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-31 Statewide Freshwater Fisheries Monitoring and Management Program