Keywords: depredation monitoring, hyperbolic location systems, passive acoustic, surface search, three-dimensional tracking, 3D tracking, false killer whales, Pseudorca crassidens, pelagic longline fishing, Coral Sea, hydrophone arrays
Application of a three-dimensional hyperbolic location system to the false killer whale (Pseudorca crassidens) depredation issue
Depredation by false killer whale (Pseudorca crassidens) is a serious problem for pelagic longline fishing in the Coral Sea. These interactions have raised substantial ecological, economic and social concerns. McPherson et al. proposed post-processing of passive acoustic recordings to analyse general odontocete acoustic behaviour and assess the effectiveness of systems being developed to reduce depredation. The location system developed to address this need utilises signal Time of Arrival Differences (TOADs) between hydrophone pairs, which confines the signal source to a hyperboloid. Through the use of a sufficient number of receivers, the resultant intersecting hyperboloids can be analysed using a 'surface search' routine to determine source location. The results presented show the capabilities of the algorithm when used with a specific hydrophone array configuration, and the practicality of use for monitoring depredation. This paper provides an overview of the techniques and discusses the adaptability of its application.