Using moored passive acoustic recorders to assess seasonal occurrence and movements of southern resident killer whales in the coastal waters of Washington State.

Abstract

Designating critical habitat is mandated for species listed under the U.S. Endangered Species Act. This task has only been partly accomplished for southern resident killer whales (SRKWs) because winter distribution is poorly understood due to a variety of factors limiting visual sightings within their known central California to northern British Columbia range. To capitalize on the unique vocal behavior of resident killer whales, including pod‐specific dialects, two types of acoustic recorders were deployed at strategic locations that span the Washington coast. Between 2005 and 2008 recorders were deployed in early winter for an average of 175.5 days at up to four sites. These functioned for an average of 114.8 days and collected a total of 47 SRKW detections. This exceeds the number of visual sightings during the same time period (15). Additionally, northern resident, transient, and offshore killer whales were recorded as well as Pacific white‐sided dolphins, and humpback and sperm whales. SRKW were detected by both types of recorders and in all areas. Detections were made between Jan. and July with the majority of these detections in Mar., Apr., and May. This new information will be of key importance to managers in meeting recovery goals.