Acoustic survey of Southern resident killer whale occurrence at the Lime Kiln hydrophone observatory, Haro Strait, Washington

Abstract

The aim of this study is to explore temporal and diurnal variation in Southern Resident Killer Whale (SRKW) acoustic activity and their relationship to other marine mammal events and to anthropogenic activity in Haro Strait, Washington. In support of the Vancouver Fraser Port Authority-led ECHO (Enhancing Cetacean Habitat and Observation) Program, six years (2016–2021) of summer/fall acoustic data from the Lime Kiln live hydrophone system (range: 10 Hz–100 kHz) in Haro Strait has been analyzed using PAMGuard software (64-bit Version: 1.15.11; Gillespie et al., 2008). Automated whistle detectors and echolocation click detectors and classifiers were parameterized to detect marine mammals, ships, and echosounders in the dataset. PAMGuard Viewer Mode was then used to review the data and mark all marine mammal and anthropogenic events. The dataset provides important long-term information on marine mammal occurrence and anthropogenic activity in a well described core area of SRKW critical habitat. Daily event logs compiled using custom R script have been used by the ECHO program to better understand the effectiveness of multi-year voluntary commercial vessel slow-downs through Haro Strait and considerable year-to-year and monthly variation in SRKW detections have been identified. Coupled with long-term day-time visual observations of SRKW, the dataset is also useful for assessing the efficacy of PAM detection mitigation methods and night-time activity levels.