Amistad Reservoir - 2007 Survey Report
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Prepared by Randy Myers and John Dennis
Inland Fisheries Division
District 1-D, San Antonio, Texas
This is the authors' summary from a 39-page report. For a copy of the complete report, use the download link in the sidebar.
Fish populations were surveyed using electrofishing (2001, 2003 and 2007), bass-only electrofishing (2005-2007), and gill nets (2004, 2006 and 2008). Creel surveys were conducted in 2002-2003 and 2007. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.
Amistad Reservoir is a 63,680 acre impoundment on the Rio Grande River. It was constructed in 1969 by the International Boundary and Water Commission and Mexico to provide water for irrigation and hydro-electric power generation. Water level in the reservoir dramatically increased in 2003-2004 resulting in substantially improved fisheries habitat. In 2007, submersed aquatic vegetation occupied 39% of the reservoir bottom (Texas side). Boat and angler access was controlled by the National Park Service (NPS) and was adequate with 11 public boat ramps. A socioeconomic survey revealed direct expenditures of Amistad anglers totaled $20.7 million in 2007.
Important sport fishes include largemouth bass, catfishes, striped bass, and white bass. Striped bass were stocked in most years since 1974. Stockings of Florida largemouth bass (FLMB) fingerlings were conducted in 2004 to take advantage improved fisheries habitat resulting from a dramatic water level increase. Angler harvest of all sport fishes has been regulated according to statewide size and bag limits. Since 2004, the NPS has regulated largemouth bass tournaments on the reservoir via a tournament permitting program.
- Prey species: Gizzard shad and sunfishes (primarily bluegill) formed the reservoir’s forage base. However, most of the gizzard shad sampled were too large to be considered potential forage for largemouth bass. Abundance of both prey species has declined in recent years, but remains sufficient to support the existing predator fish populations.
- Catfishes: The catfish community is dominated by channel catfish. Blue and flathead catfish are present, but in low numbers. Channel catfish abundance increased slightly during the study period. Angling effort directed at catfishes was substantially lower in 2007 compared to in 2002-2003.
- White bass: Abundance of white bass was greater in 2008 than in previous years, with most fish in the population exceeding the 10-inch minimum length limit. However, angling effort directed at this species was substantially lower in 2007 than in 2002-2003.
- Striped bass: Abundance of striped bass was slightly greater in 2008 than in previous years, with most fish in the population exceeding the 18-inch minimum length limit. Angling effort directed at this species was slightly lower in 2007 than in 2002-2003.
- Largemouth bass: Strong year classes of largemouth were produced in 2003 and 2004 coincident with the 2003-2004 dramatic water level increase. This yielded an improved population which supported a popular fishery. Angling effort in 2007 was nearly double compared to 2002-2003.
Continue to provide a striped bass fishery supported by annual stockings. Examine possible management activities to maintain the high quality largemouth bass fishery including evaluating the potential impacts of reducing the largemouth bass bag limit from 5 to 3 fish. Conduct approved special research project to determine optimum treatment techniques for alleviating decompression illness common to tournament caught fish at the reservoir.
Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-33 Statewide Freshwater Fisheries Monitoring and Management Program