A comparison of EAR and SoundTrap performance for acoustic monitoring of resident killer whales

Abstract

Since 2006, a network of hydrophones has been deployed along the outer coasts of Washington, Oregon, and California to improve our understanding of endangered Southern Resident killer whale (SRKW) movements outside the inland waters of the Salish Sea and refine Critical Habitat designation. During this time period, improvements in methods and equipment have resulted in longer deployments, improved ability to detect resident killer whales (RKW) and monitor their acoustic behavior, and added the capability to characterize ambient and ship noise throughout SRKW range. It is important to understand how these changes might impact the results of long term studies on RKW movements and distribution. In this study, we co-located Ecological Acoustic Recorders (EARs) and SoundTraps at five locations along the Washington coast, analyzed each data set separately, and compared the results. Preliminary analysis of these data resulted in a 1.6 to 3.4 times increase in the number of days with RKW detections in the SoundTrap data compared to the EAR data depending on location. We will present the results of this comparison, investigate potential causes of the differences between recorder type, and highlight the implications of these differences to previous knowledge of RKW movements along the Washington coast.