Spring influenced streams in texas harbor at least 13 endemic fishes ostensibly because these species require stable thermal regimes testing this requirement and forecasting vulnerability to thermal…

The U.S. Fish and Wildlife Service (USFWS), Region 2, awarded the Texas Parks and Wildlife Department (TPWD) a formula grant of $191,640 under the State Wildlife Grants (SWG) Program (CFDA 15.634) for the period January 1, 2026 through December 31, 2027. This award supports comprehensive field monitoring and laboratory research to assess thermal regime requirements and climate vulnerability for six spring-associated fish species of greatest conservation need (SGCN) in Central Texas. The project builds upon existing TPWD efforts that have generated 65 million water temperature measurements across 168 monitoring stations since 2022.

The deliverables include reconfiguration and expansion of the existing temperature monitoring network to three new drainage basins, establishment of 12 additional water level monitoring stations as surrogates for spring discharge measurements through December 2027, and refined statistical models to forecast climate change and groundwater depletion effects on spring-fed stream thermal regimes. TPWD has subawarded a portion of funding to the University of Texas at San Antonio (UTSA) to conduct complementary laboratory experiments quantifying metabolic scope and thermal optima for the six SGCN fishes. These integrated field and laboratory products will provide enhanced understanding of species thermal ecology and support evidence-based conservation strategies to prevent thermal regime degradation in Texas' endemic spring-fed aquatic ecosystems.

Spring influenced streams in texas harbor at least 13 endemic fishes ostensibly because these species require stable thermal regimes testing this requirement and forecasting vulnerability to thermal regime degradation can be accomplished by integrating field temperature monitoring with laboratory physiology measurements thermal regimes in spring FED streams are driven by temporal variation in air temperature and spring discharge which varies with interannual climate fluctuations current tpwd funding has produced 65 million water temperature measurements across 168 monitoring stations in central texas since 2022 and represent three years of hot and dry climatic conditions at the same time tpwd has funded laboratory research that has characterized acclimation capacity as well as acute and chronic upper thermal tolerances for six spring associated species of greatest conservation need sgcn fishes we proposed to reconfigure and optimize the distribution of existing temperature monitoring stations establish new stations in three new drainage basins and begin monitoring water levels a surrogate for discharge at 12 of these stations through december 2027 this additional spatiotemporal coverage will capture greater variation in water temperature spring flow as well as the causal landscape and climatic drivers these data will be used to refine statistical models to more accurately map and forecast effects of climate change and groundwater depletion on the thermal regimes of spring FED streams we also propose additional laboratory experiments to quantify metabolic scopes which will expand our understanding of physiology from upper tolerance limits to include thermal optima for the six fishes because summer water temperatures are inherently closer to thermal optima than to upper tolerance we hypothesize that thermal optima limit the distributions of these species to springs and drive vulnerability to warming temperatures these physiology data will be integrated with the maps of thermal regimes to 1 test the hypothesis that stable thermal regimes are essential to the population persistence of spring associated fishes and 2 forecast vulnerability to scenarios of climate change and spring flow depletion this information will inform the management of ecologically significant stream segments on the edwards plateau and in the middle RIO grande basin as well as the conservation of six sgcn fishes as outlined in the 2023 texas state wildlife action plan tpwd 2023