Gulf of Alaska | Mammals MASTER’S ORAL PRESENTATION Acoustics of Cook Inlet beluga whales and anthropogenic noise in lower Cook Inlet rivers Presenter: Sonia Kumar , svkumar@alaska.edu, University of Alaska Fairbanks Manuel Castellote , manuel.castellote@noaa.gov, Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA Anthropogenic disturbance in Cook Inlet is steadily growing, with much of it attributed to resource exploration and extraction, world-renowned sport, commercial, and subsistence fisheries, and cargo shipping. These waters also provide habitat for the endangered Cook Inlet beluga (CIB) whale ( Delphinapterus leucas ), which use a variety of vocalizations to communicate, hunt, and navigate. Passive acoustic monitoring (PAM) is a non-invasive tool to detect underwater acoustic sources, both anthropogenic and natural. In 2021 and 2022, we utilized PAM in the Kenai and Kasilof rivers to monitor the acoustic presence of CIB. Acoustic presence data were then correlated with anthropogenic and environmental noise in each river. Two types of instruments were used, F-PODs and SoundTraps. F-PODs were programmed to log CIB echolocation frequencies between 20 kHz – 160 kHz. SoundTraps (ST-500 and ST-600) were programmed to record the entire underwater soundscape at frequencies between 20 Hz – 24 kHz. The acoustic recordings from SoundTraps were visually assessed in long-term average spectrograms in Raven Pro and half hour time frames were characterized into one of four bins, low, medium, loud, and thunderous noise. CIB acoustic presence was then correlated with the anthropogenic and environmental sound categories. Shore based visual surveys were conducted to monitor the number and type of boats in each river, other marine mammals, and CIB behavior to compare with PAM detections. The F-PODs in the Kenai River recorded decreasing proportions of beluga positive minutes the further upriver they were placed. There were 147 days when at least one F-POD in the Kenai River was logging data. The F-POD at the mouth of the river had a beluga acoustic detection rate of 1.67%. The middle F-POD had a beluga acoustic detection rate of 1.44%, and the F-POD furthest upriver had a beluga acoustic detection rate of 0.17%. There were 103 days when at least one of the two F-PODs in the Kasilof River was logging data but CIB were neither acoustically nor visually detected at that river in 2021 during this study. Based upon the 2021 Kenai data, CIB presence was significantly lower at the loud noise category than at the low noise category. A comparison between years will examine how noise levels might have changed and if differences in CIB presence were observed. Verena Gill , verena.gill@noaa.gov, NOAA Fisheries Curry Cunningham , cjcunningham@alaska.edu Lara Horstmann , lara.horstmann@alaska.edu, University of Alaska Fairbanks
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