Towards collective circum-antarctic passive acoustic monitoring: the southern ocean hydrophone network (SOHN)

The Southern Ocean Research Partnership (SORP) is an international research program initiated within the International Whaling Commission (IWC) in 2009 to promote collaborative cetacean research, develop nov el research techniques, and conduct non-lethal research on whales in the Southern Ocean (CHILDERHOUSE 2009). One of the original research projects of the SORP is the Blue and Fin Whale Acoustic Trends Project, which aims to implement a long term passive acoustic research program to examine trends in Antarctic blue (Balaenoptera musculus intermedia) and fin whale (B. physalus) abundance, distribution, and seasonal presence in the Southern Ocean through the use of a network of passive acoustic recorders: the Southern Ocean Hydrophone Network (SOHN). Networks of widely spaced passive acoustic recorders can provide insights in spatio-temporal patterns of the presence and properties of whale calls as well as the potential to monitor trends in Antarctic blue and fin whale abundance. The SOHN will consist of a network of autonomous underwater acoustic re cording stations surrounding the Antarctic continent with each site remaining active throughout the 10-year duration of the project. In addition to circum polar coverage, high priority will be given towards achieving simultaneous temporal coverage, especially in the early years of the project. While logis tical constraints may prevent uniform distribution of SOHN recording sites around the continent, the Acoustic Trends Working group (ATW) aims to have at least one recording site in each of the six IWC management areas (i.e., one per 60° longitudinal wedge). International collaboration and coordination are imperative to achieve the project goals due to the high cost of Antarctic research as well as the broad spatial and temporal scales over which the SOHN will span. Furthermore, standardization of data is paramount for accurate and efficient analysis and interpretation of SOHN data. To facilitate international participation in the SOHN, this document provides practical recommendations to guide and support passive acoustic data of project as well as technical and logistic information and recommendations regarding standardization of recording locations is provided here for a diverse collection in Antarctic waters. This whitepaper addresses a wide audience, ranging from scientists from different disciplines with access to instrumenttation and/or infrastructure to collect passive acoustic data in the Southern Ocean, to ship operators or other parties that can provide logistic support to make the SOHN a reality. Background information and an outline of the sci entific aims of project as well as technical and logistic information and re commendations regarding standardization of recording locations is provided here for a diverse audience coming from different backgrounds with widely differing levels of experience with the applications and use of passive acoustic instrumentation. By providing the information relevant for SOHN from the ground up, we aim that this document contributes to increase aware ness and participation by a broad range of partner nations and organizations in the SOHN and Acoustic Trends Projects.