ABSTRACT: Recently, sudden collisions between large cetaceans and high-speed hydrofoils have become problematic to Japanese sea transport in some localities. We therefore initiated a project to investigate approaches for minimizing risk to both ships and cetaceans. Under the present project, the following three subprojects are underway: clarifying which whale species are found near sea routes and determining their seasonal variations; identifying whale species that have a high collision risk; and determining the unique acoustic characteristics of high-collision-risk cetaceans for the improvement of underwater speakers (UWS). By conducting acoustic surveys using novel methods, including an anatomical approach based on characteristics of the inner ear, the aim of this project is to accurately estimate the audible range of species with a high collision risk and improve the sounds generated by the UWS. Thus far, we have identified the cetacean species at high-risk in two major sea routes. In the next phase of the study we plan to develop an imaging system that recognizes a cetacean's unique blow using an infrared camera, in an attempt to warn of the approach of high-collision-risk whale species at an early stage by sounding an alarm.

KEYWORDS: Safety at Sea, Collision Avoidance, Hydroacoustics, Hydrofoils, Cetaceans, Collision Risk, High Speed Craft (HSC), Underwater Speaker (UWS)

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