Seasonal and spatial patterns of cetacean occurrence off Oahu, HI observed acoustically.

Abstract

The seasonal occurrence and distribution of cetaceans around island archipelagos is often poorly understood. This is generally due to the variability in sea surface conditions associated with islands, which make visual surveys prohibitive along exposed areas and/or during seasonal periods of rough seas. Historically, this has been the case for many cetacean species found in Hawaiian waters. Recently, however, concerns about the impacts of anthropogenic activities have created a need to better understand the long‐term, spatial and temporal distributions of cetaceans in the archipelago. To meet this need, an effort was begun in February 2009 to study cetacean occurrence around the island of Oahu using a network of passive acoustic recorders. Five ecological acoustic recorders (EARs) were deployed in waters 115–575 m deep along the perimeter of the island and refurbished approximately every 4 months. Data from these deployments are providing an unprecedented perspective on the occurrence of both odontocete and mysticete cetaceans around the island. The southeastern corner of Oahu, in particular, has emerged as a hotspot of odontocetes; diversity and abundance. This and two other sites being monitored have historically received little or no visual survey attention, but are clearly important habitats for a variety of species.