Passive acoustic monitoring of Japanese spiny lobster stridulating sounds

Abstract

The Japanese spiny lobster Panulirus japonicus is an important marine resource in Japan. In order to manage its stock, an effective methodology for population assessments is needed. In this study, we focused on the stridulating sounds produced by spiny lobsters. The stridulating sounds are widely accepted to function as an anti-predator signaling, for potential use in monitoring lobster stocks remotely. An underwater sound recorder was attached on gill nets or lobster pots around Izu Oshima and Niijima islands, within the Izu archipelago, Tokyo, Japan, where lobster fishing is common. Stridulating sounds were manually extracted from each data file. The frequency of stridulating sounds tended to increase on nights with a large tidal change. There was a positive correlation between the frequency of stridulating sounds and the number of lobsters caught in the net or lobster pot. Even in trials where no lobsters were caught, several stridulating sounds could be detected and increased at night. In this study, we describe the sound characteristics of the stridulation, and the trend of nocturnal call productions of this species. This study is the first step towards passive acoustic resource monitoring of Japanese spiny lobsters, which were quite difficult to estimate the density of remotely.