Energetic Implications for Guadalupe Bass, Micropterus trecullii, Management Under a Projected Climate Change Scenario

Authors: Gabriel Murillo, Preston Bean, Nate Smith, Mitch Nisbet, Matthew Troia

Year: 2024

Abstract

The Guadalupe Bass, Microperus treculii, is an imperiled endemic species that is designated as the state fish of Texas. There is a lack of physiological knowledge regarding the effects of temperature on Guadalupe Bass behavior and physiology. To fill this knowledge gap, routine respiration (Rrout) and maximum consumption (Cmax) were measured across a range of temperatures in the lab. Cmax was quantified by feeding Guadalupe Bass (n=56) ad libitum rations of Western Mosquitofish, Gambusia affinis, over three days. Rrout was quantified via intermittent flow respirometry (n=48). The difference between Cmax and Rrout was the energy balance (J/g/day) available for maintenance, growth, and reproduction. A generalized additive model was used to quantify the relationship between energy balance and temperature, ultimately predicting net energy balance based on contemporary temperatures observed at a representative stream within the Guadalupe Bass range. The model was then used to project net energy balance at elevated temperatures (+2ºC) representing a future climate change scenario. Cmax exceeded Rrout across all temperatures with Cmax following a hump shaped curve peaking at 32ºC then decreasing, whereas Rrout followed an exponential curve. Under both contemporary and elevated temperatures, Guadalupe Bass had an energy surplus throughout the entire year. Energy surplus across all seasons was 16.4% higher under increased temperatures relative to contemporary temperatures. Additionally, winter and summer energy surplus was 35.9% and 3.58% higher under elevated temperatures relative to contemporary temperatures, respectively. Increased energy surplus suggests that Guadalupe Bass will have more energy for maintenance, growth, and reproduction ultimately benefiting individuals and populations assuming that consumptive demands are met by prey availability. The results from this experiment and additional mass dependent experiments will be used to parameterize a bioenergetics model that will predict growth under different climate scenarios ultimately informing Guadalupe Bass management.