Behavior and habitat selection of largemouth bass in response to dynamic environmental variables with a focus on dissolved oxygen
Stratification is a naturally occurring phenomenon in many lakes and reservoirs that is often aggravated by increasing agricultural land use. During summer stratification, substantial production regularly leads to hypoxic areas below the thermocline, resulting in the loss of suitable fish habitat. Additionally, high surface temperatures can also contribute to the loss of preferred habitat. Understanding how fish interact with and respond to their environment is a critical part of fisheries research and management. My research investigates the effects that low dissolved oxygen concentrations and other dynamic environmental variables have on behaviors and distributions of largemouth bass, Micropterus salmoides a popular sportfish. To better understand how largemouth bass respond to low oxygen concentrations, I performed three separate, complementary studies. First, I observed foraging behavior of juvenile largemouth bass in simulated stratified environment. Observations provided significant evidence that low dissolved oxygen concentrations may restrict access to prey resources below the thermocline. Additionally, I observed several behavioral modifications while fish were foraging in low oxygen environments. Second, I tracked largemouth bass positions in a stratified lake and examined oxygen and temperature selection along with movements in relation to available abiotic habitat. I found that largemouth bass generally selected favorable oxygen concentrations and temperatures, and were able to occupy areas of suitable habitat despite large portions of the water column containing areas of low oxygen concentrations or high temperatures. However, there were individuals from the tagged population frequently observed in low oxygen environments. Distributions of fish are influenced by a host of dynamic environmental variables and their interactions. Considerations of biotic and physical variables in addition to abiotic variables such as oxygen concentration and temperature are necessary for a complete understanding of fish habitat selection. Thus, I conducted analyses to determine the effects and relative influence of multiple abiotic, biotic, and physical variables on the occurrence of largemouth bass. I found that oxygen concentration and temperature had the most influence on largemouth bass occurrence. Depth, along with interactions with oxygen and temperature also had substantial influence on occurrence. Largemouth bass were positively associated with woody structure, but negatively associated with vegetated habitats. Bottom slope and prey density were also found to have a slight influence on occurrence. Collectively, my results suggest that summer stratification has the potential to significantly influence largemouth bass behaviors and distributions in lakes and reservoirs principally through the avoidance of low dissolved oxygen concentrations.
Largemouth Bass, Oxygen, Hypoxia, Behavior, Movements
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations
University of Illinois at Urbana-Champaign