Comparative effects of auditory and visual disturbances on parental care behaviors of smallmouth bass

A prevalent source of sensory pollution in freshwater ecosystems is recreational motorboats, that impacts freshwater fish through several mechanisms. Auditory and visual sensory disturbances are of particular importance as fish use these cues during critical reproductive behaviors such as parental care. To understand how sensory noise disrupts behavior, we conducted a field-based study to examine how auditory noise and visual cues impact smallmouth bass ( Micropterus dolomieu ) parental care behaviors. Smallmouth bass were exposed to two sequential treatments: auditory noise and visual disturbances. During auditory disturbances, smallmouth bass were exposed to playback noise recordings, while during visual disturbances smallmouth bass were exposed to a solid object moving in their visual field. Each disturbance treatment consisted of three phases: a five-minute pre-disturbance phase, a one-minute disturbance exposure phase and a five-minute post-disturbance phase. Our findings indicate bass were most aggressive during the pre-visual disturbance phase (p = 0.02) and spent more time swimming off the nest after both auditory and visual disturbances (p = 0.017). Further, bass altered their behavioral repertoire. During and immediately following a visual disturbance, smallmouth bass increased percentage of time spent stationary on the nest (37% and 46%, respectively) compared to the pre-disturbance phase (32%). Conversely, when exposed to auditory disturbances, bass increased time spent swimming off the nest (72%) compared to the pre-disturbance phase (50%). Our results demonstrate that visual and noise disturbances affect smallmouth bass behaviors differently. This suggests an integrated approach must be considered to truly understand the impact of motorboat activity.