Long-Term Trends of Striped Bass Habitat Suitability Under a Temperature-Oxygen Squeeze in Lake Texoma, Oklahoma and Texas

Abstract

Warmer epilimnetic water temperatures and reduced dissolved oxygen levels in deeper water are common stressors for fishes in freshwater reservoirs throughout the summer. We investigated the effects of a temperature–oxygen squeeze - a phenomenon that squeezes fish into a narrow, livable zone - on striped bass from 1995 to 2020 in Lake Texoma. This reservoir is located on the border of Texas and Oklahoma, possesses one of the largest self-sustaining populations of inland freshwater striped bass in the US, and is of high economic importance to the region. We used a trait-based approach to quantify 1) how the total volume of suitable habitat for striped bass has changed seasonally and across years, 2) the relative influence of temperature and oxygen on habitat suitability, and 3) whether a temperature-oxygen squeeze has affected the striped bass population and body condition. We found that the volume of suitable habitat for striped bass decreased over the course of each summer and was greatly influenced by day-to-day persistence and water level, but did not exhibit a significant linear decline over the years from 1995 to 2020. Additionally, the relative influence of temperature and oxygen on habitat suitability varied depending on the thresholds used to define the temperature-oxygen squeeze. We found no significant linear relationships between habitat volume, striped bass population, and body condition. One hypothesis that would explain this null result is that striped bass in Lake Texoma may be adapted to the seasonally stratified conditions, especially since habitat volume did not show a monotonic decline over time. We also detail other biophysical and statistical hypotheses that might explain why we did not detect an effect of a temperature-oxygen squeeze on striped bass. This study provides insights into future management of Lake Texoma and other reservoir fisheries as global change alters patterns in temperature, oxygen, and reservoir habitat.