Ocean acoustic observing platforms for marine creatures around Japan

Many animals in the ocean produce sounds for mating choice, territorial defending, group cohesion and echolocation. Sound travels much longer distance in the water comparing with light that makes the acoustic waves efficient for long distance communication and sensing. The species or family specific sounds can be used to identify not only the presence of animals but also counting the number and density of target species. In these years, various types of underwater recorders are available. However, for the successful acoustic monitoring in the ocean, safe platforms to deploy the recorders are essential. In this paper, advantages and drawbacks of fixed and mobile platforms for passive acoustic monitoring are summarized referring practical application examples in Japanese waters.