Impacts of vessel noise on Red Drum (Sciaenops ocellatus) spawning choruses in Saint Andrew Bay, Florida, U.S.A.

Noise pollution is an increasing threat to soniferous fishes, however, research on noise pollution impacts is limited to few species and rarely studied in situ. Red Drum (Sciaenops ocellatus) is an estuarine, fishery species that choruses during spawning. We tested predictions of the hypothesis that Red Drum alter sound production in response to vessel noise. We used passive acoustic monitoring in 2021 and 2022 at an estuarine inlet and Generalized Least Squares (GLS) models to assess vessel equivalent continuous sound levels (Leq) and other abiotic parameters on Red Drum chorus Leq. GLS models of daily crepuscular choruses indicated a significant reduction of 0.05dB in Red Drum Leq in relation to every 1dB of crepuscular vessel noise in 2021 (p = 0.026). GLS models testing influence of abiotic variables and prior vessel noise, predicted reduced chorus Leq proportional to prior noise Leq: ca. 0.05dB and 0.04dB reduction for every 1dB of vessel Leq in 2021 and 2022, respectively. In some instances, Leq during vessel noise was lower than fish chorus Leq immediately prior, indicating instances when fish reduced chorus amplitude during vessel noise or fled the immediate area. In cases when Leq of vessel noise periods exceeded fish calling Leq immediately prior, it is not known if fish modulated calling amplitude because the portion of combined vessel noise and fish chorus amplitude from vessels is unknown. In peak spawning season (September-October) vessel noise was frequent, detected in >31% of recordings in both years and up to 100% of recordings on some dates. Observations of disrupted choruses and high vessel noise prevalence suggest spawning behavior may be impacted by abundant vessel noise.