Amistad Reservoir - 2011 Survey Report

Prepared by Randy Myers and John Dennis
Inland Fisheries Division
District 1-D, San Antonio, Texas

This is the authors' summary from a 40-page report. For a copy of the complete report, use the download link in the sidebar.

This report summarizes results of surveys conducted from July 2008 to June 2012 and contains a management plan for the reservoir. Fish populations were surveyed using electrofishing and gill nets. A six-month duration creel survey and two vegetation surveys were also conducted.

Reservoir Description

Amistad Reservoir is a 63,680 acre impoundment on the Rio Grande River. It was constructed in 1969 and managed by the International Boundary and Water Commission to provide water for irrigation and hydro-electric power generation. During the study period, water level increased from 20 feet low, remained within 5 feet of full pool for about three years, then decreased to about 20 feet low. Abundance of submersed aquatic vegetation declined substantially during the study period. Boat and angler access is excellent; the National Park Service (NPS) maintains 11 public boat ramps.

Management History

Important sport fishes include largemouth bass, catfishes, striped bass, and white bass. Striped bass were stocked in most years since 1974. Florida largemouth bass (FLMB) were stocked periodically from 1975 to 2006 and annually since 2008 to improve FLMB introgression and trophy largemouth bass potential. 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 via a tournament permitting program.

Fish Community

• Prey species: Gizzard shad and sunfishes formed the reservoir’s forage base. Most of the gizzard shad sampled were too large to be considered potential forage for largemouth bass. Abundance of gizzard shad and bluegill has declined in recent years, but forage remains sufficient to support the existing predator fish populations.
• Catfishes: Channel, blue, and flathead catfish are present in the reservoir in low abundance. Angling effort directed at catfishes remains low and accounted for 1.1% of total angling effort in the reservoir according to 2012 creel survey studies.
• White bass: Abundance of white bass during 2008-2012 exceeded historic average abundance. Angling effort directed at white bass remained low, accounting for 1.3% of total angling effort in 2012.
• Striped bass: Abundance of striped bass during 2008-2012 was below historic average abundance. Angling effort directed at striped bass remained low, accounting for 0.2% of total angling effort in 2012.
• Largemouth bass: Abundance of largemouth bass peaked in 2009 and then decreased to below the historic average in 2011. However, abundance of fish >14 during the 2008-2012 study period remained above historic average abundance. Nearly all (95.2%) of the angling effort at the reservoir was directed for largemouth bass during 2012, of which 32.9% was tournament angling. Five ShareLunker fish were contributed from the reservoir during 2008-2012.

Management Strategies

Continue to provide a striped bass fishery supported by annual stockings. Continue stocking Florida largemouth bass on an annual basis to maintain high Florida bass introgression and production of trophy fish.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-221-M-2 Statewide Freshwater Fisheries Monitoring and Management Program