Medina Reservoir - 2020 Survey Report

Prepared by Mitchell Nisbet
Inland Fisheries Division
San Antonio District

This is the author's summary from a 29-page report. For a copy of the complete report, use the download link in the sidebar.

Fish populations in Medina Reservoir were surveyed in 2019 and 2021 using gill netting and in 2020 using electrofishing. Historical data are presented with the 2019-2021 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

Medina Reservoir is a 5,410-acre impoundment located on the Medina River in the San Antonio River Basin in Medina and Bandera counties, Texas. The reservoir experienced a considerable water level increase in 2015, filling to conservation pool elevation from 80 feet low. Subsequently, the reservoir water level dropped, then refilled again in late fall 2018. Since that time, the reservoir water level has dropped to approximately 36 feet low. Most of the shoreline is characterized as rock bluff or rocks and gravel. Flooded terrestrial vegetation is currently the predominant fisheries habitat type. In February 2021, zebra mussels were discovered in the reservoir, and since have established a population.

Management History

Important sport fish include Largemouth Bass, Hybrid Striped Bass, and White Bass. All species have been managed under statewide regulations. Florida Largemouth Bass fingerlings have been stocked most recently in 2016 when fisheries habitat was optimal for survival. Palmetto Bass have been stocked on an irregular basis due to variable availability and water level fluctuations and were most recently stocked in 2017 and 2018. Sunshine Bass were stocked in 2020. Texas Parks and Wildlife Department (TPWD) sent out a news release in March 2021 alerting constituents that zebra mussels were discovered in the reservoir and again in June 2021 that the lake was classified as infested.

Fish Community

• Prey species: Gizzard Shad and sunfish spp., primarily Bluegill, comprise the prey community. Threadfin Shad were present in the reservoir, in low relative abundance. Gizzard Shad relative abundance peaked and then declined following the refilling of the reservoir. Bluegill relative abundance has also decreased since 2016. In combination with declining water levels, prey species abundance could be a limiting factor contributing to reduced populations of some predator species.
• Catfishes: Both Blue and Channel Catfish relative abundance has remained consistently low. Population size structures for both catfish spp. likewise has remained consistent. Channel Catfish greater than 20 inches and Blue Catfish over 40 inches are available to anglers.
• Temperate basses: White Bass relative abundance was higher in 2019 and 2021 compared to previous years. Most fish collected in 2019 and all fish collected in 2021 exceeded 10-inches and were available for harvest. Hybrid Striped Bass relative abundance was greatly increased in 2021 and was the highest recorded for the lake. Hybrid Striped Bass up to 24 inches were available to harvest.
• Largemouth Bass: Relative abundance of Largemouth Bass in 2020 was similar to in 2016. Very few legal-length fish were available to anglers. Largemouth Bass had poor growth (average age at 14 inches long was 4.1 years) and were in poor condition (low relative weights).

Management Strategies

• Continue to maintain and promote the Hybrid Striped Bass fishery by stocking 5-15 fish/acre when the water level is within 25 feet of conservation pool.
• Educate the public about the negative impacts of aquatic invasive species, monitor and record potential impacts of zebra mussels on sport fish in the reservoir, and install zebra mussel stencils on the public boat ramp and main private boat ramp.
• Conduct general monitoring surveys using gill nets and electrofishing in 2024-2025.
• Access and vegetation surveys will be conducted in 2024.

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