H-4 (Gonzales) Reservoir - 2003 Survey Report

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Prepared by John Findeisen and Aaron Walters
Inland Fisheries Division
District 1-E, Mathis, Texas

This is the authors' summary from a 22-page report. For a copy of the complete report, use the download link in the sidebar.

H-4 Reservoir was surveyed in the fall 2003 using frame nets and electrofishing and in the spring 2004 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

H-4 is a 696 acre mainstream reservoir on the Guadalupe River in Gonzales county. The reservoir was impounded in 1931 to provide water for a hydroelectric plant. The substrate is composed primarily of silt, sand, clay, and some gravel and rock. Angler and boat access was limited. There are no public ramps and the one private, pay-to-use, ramp was open. There were no handicap specific facilities. At the time of sampling, the habitat was primarily boat docks, stumps, floating-leaf vegetation and limited submerged and emergent vegetation. Nuisance aquatic vegetation has historically created access problems in the reservoir. Water hyacinth, which had become a severe problem in 2001, covered 0.4 acres in 2003. Hydrilla was observed in 2001 and 2003 only at the boat ramp. Water hyacinth had become the dominant plant species in 2001, covering many of the areas where native aquatic vegetation is normally found.

Fish Community

• Prey species: The 2003 electrofishing catch rate of gizzard shad and threadfin shad was 68.0/hr and 76.0/h, respectively. The gizzard shad catch rate increased previous years. The Index of Vulnerability (IOV) for gizzard shad was 37, indicating that 37% of the gizzard shad collected were less than eight inches in length, available to most predators, and that the gizzard shad population is dominated by larger fish. Threadfin shad provide an adequate alternative for the lack of small gizzard shad. The 2003 electrofishing catch rate for bluegill and redear sunfish was 213.0/hr and 48.0/hr, respectively. The bluegill catch rate increased from previous years. In the past, sunfish species provided a potential fishery as catch rates of quality fish and larger were relatively high. However, due to the loss of valuable centrachid habitat via large floods and water hyacinths, the quality of the sunfish fisheries in H-4 reservoir was well below average in 2003.
• Channel catfish: The 2004 gill net catch rate of channel catfish was 30.8/NN, substantially greater than in 1996 (1.8/NN) and 1999 (3.2/NN). Channel catfish of stock size and greater exhibited above average condition, as mean relative weights were over 100.
• Largemouth bass: The 2003 electrofishing catch rate of largemouth bass was 29.0/hr, higher than 2001 (4.0/h) but below 1999 (69/h). Very few fish of stock size or greater were collected, possibly due to weak year classes produced as a result of habitat loss from large floods and water hyacinths. Largemouth bass stock size and greater exhibited above average condition, as mean relative weights were near 100. Largemouth bass reached legal size between ages 2 and 3. Electrophoresis indicated an 80% frequency of Florida largemouth bass alleles, with 53% of the population having Florida largemouth bass genotype.
• White crappie: The 2003 trap net catch rate for white crappie was 11.3/NN, higher than both 1999 and 2001. One net caught 72 of 90 total white crappie collected during the survey. Both PSD and RSD-P indicate the population is dominated by larger fish, with 44% of the stock size or greater fish being legal size. White crappie stock size and greater exhibited above average condition, as mean relative weights were near 100. In 1999, white crappie reached legal size by age 2. Habitat loss from large floods and water hyacinth appears to have impacted the crappie population in 2001.

Management Strategies

• Based on current information, the reservoir should continue to be managed with existing regulations.
• Currently the only access to H-4 Reservoir is through a private, pay to use, boat ramp. Work with GBRA on building a new public boat ramp and improving bank access.
• Hydrilla, water hyacinth, and water lettuce have historically created access problems throughout the reservoir. Work with GBRA on controlling nuisance aquatic vegetation before problems arise.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-29 Statewide Freshwater Fisheries Monitoring and Management Program