Interactions between walleye and largemouth bass in a West Texas reservoir

Many reservoirs in the southwestern United States develop an oxygen-deficient hypolimnion below a well-defined thermocline due to their deep nature and warm ambient temperatures. Such conditions may force the walleye (Stizostedion vitreum vitreum), a species recently introduced in the Southwest, into habitat more commonly occupied by the major resident predator, the largemouth bass (Micropterus salmoides). Seasonal changes and overlap in habitat use by these two species was investigated in Lake Mackenzie, Texas using ultrasonic telemetry. Habitat use by each species varied seasonally. Largemouth bass were found primarily in brushy coves during fall, winter, and spring, but increased their use of rocky shoreline areas during the summer. Walleye used primarily rocky shoreline areas and open-water habitats throughout the year, but this use changed on a seasonal basis. Most walleyes were located in open water during times that deep-water oxygen content was suitable for the species. Walleye use of rocky shoreline areas peaked in summer when hypolimnetic oxygen was at a minimum. Overlap in habitat use by walleyes and largemouth bass was greatest during the summer but probably was not extensive enough to limit the production of either species. Knowledge of these seasonal movements also should be helpful to anglers.