Amistad Reservoir - 2016 Survey Report

Prepared by Randall A. Myers and John A. Dennis
Inland Fisheries Division - San Antonio District

This is the authors' summary from a 32-page report. For a copy of the complete report, use the download link in the sidebar.

Fish populations in Amistad Reservoir were surveyed in 2016 and 2017 using electrofishing and in 2017 using gill netting. Historical data are presented with the 2016-2017 data for comparison. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.

Reservoir Description

Amistad Reservoir is a 63,680 acre Texas-Mexico border impoundment on the Rio Grande River. It was constructed in 1969 and is managed by the International Boundary and Water Commission to provide water for irrigation and hydro-electric power generation. Boat and angler access is excellent. The National Park Service (NPS) maintains 9 public boat ramps. Water level averaged 25 feet below conservation pool elevation (CP) since spring 2015, however it remained relatively stable fluctuating just 11 feet since then which contributed to the expansion of aquatic plants. Occurrence of aquatic vegetation, primarily hydrilla and pondweed spp., was 35.8% in 2016.

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 2008 and annually since 2010 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 and quantified black bass tournaments via a mandatory tournament permitting program.

Fish Community

• Prey species: Gizzard Shad, Threadfin Shad, and sunfish spp. comprise the prey community. As a group, these species were sufficiently abundant and sufficiently sized to support existing predators.
• Catfishes: Channel, Blue, and Flathead catfishes were present in low numbers. Gill net catch-per-unit-effort (CPUE) ranged from 0.2 to 1.1 fish/net-night(nn) in 2017.
• White Bass: Gill net CPUE was 1.6 fish/nn in 2017. The majority of White Bass collected (80%) exceeded the 10-inch minimum length limit.
• Striped Bass: Gill net CPUE was 2.9 fish/nn in 2017. The majority of Striped Bass collected (79%) exceeded the 18-inch minimum length limit.
• Black basses: Largemouth Bass abundance has increased according to recent spring samples which are likely due to expanding aquatic plant coverage. Likewise, growth has increased compared to previous estimates. Smallmouth Bass abundance was low (electrofishing CPUE =2.5 fish/h).
• White Crappie: This species is present in the reservoir, but in low abundance. Gill net CPUE was 0.4 fish/nn in 2017.

Management Strategies

• Continue stocking Striped Bass at 3-5 fish/acre annually to maintain the fishery.
• Continue to annually stock Florida Largemouth Bass at 1,000 fish/km of shoreline to enhance trophy potential.
• Inform the public about the negative impacts of aquatic invasive species, and monitor for presence of aquatic invasive species during routine fish population and habitat surveys.
• Work cooperatively with reservoir management agencies in performing outreach and addressing issues.

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