Doctor of Philosophy (PhD)
Noise pollution is pervasive to nearly all aquatic and terrestrial ecosystems and was labeled a pollutant of global concern by the World Health Organization in 2011. In the past few decades, underwater ambient noise levels have risen almost 30 dB SPL re: 1 µPa in the frequency range that most fish produce and detect acoustic stimuli due to rises in shipping, oil exploration, and pile driving. Changes to the natural soundscape can impact almost all aspects of an animal’s life. My dissertation research takes an integrative, whole-animal approach to examining how increased background noise impacts fish behavior, physiology, development, and communication. First, I found that social interactions occurring in noisy conditions were less effective. Males spent more time distracted or stressed during territorial fights, resulting in a longer time to fight resolution. Males also changed when and how they courted gravid females. Female hearing capabilities were significantly reduced following noise exposure. Changes to male signal production, female detection capabilities, and possibly the signal itself all interfere with effective social communication. Cumulatively, this resulted in a lower incidence of spawning during noise. Noise exposure also hindered mouthbrooding and maternal care behaviors. Females exposed to noise during brooding were more likely to cannibalize or prematurely release under-developed juveniles. Juveniles that were exposed to noise during development had lower growth rates, higher mortality, and altered social and startle behaviors. Finally, I found that fish possess all components of the proposed inner ear CRF-signaling system and that its expression is mediated by sex, reproductive state, and noise exposure. Because noise-induced changes in expression are dependent on physiological state, it is possible that noise-induced threshold shifts could also be modulated by reproductive condition. Overall, these results provide one of the most comprehensive whole-animal pictures on how increased background noise impacts fish. By examining subtle, sub-lethal changes to behavior, physiology, and communication, we can better inform conservation efforts before human-influenced noise levels reach potentially lethal levels.
Butler, Julie, "The Impact of Anthropogenic Noise on Fish Behavior, Communication, and Development" (2019). LSU Doctoral Dissertations. 5086.