Analysis of ship noise around a dugongs' habitat

Abstract

Dugongs, Dugong dugon, are listed in the Red List of IUCN (The World Conservation Union) as a vulnerable species (VU). It is important that we evaluate effects of ship noises on dugongs for peaceful coexistence between humans and dugongs. There is no quantitative study that evaluated the response of the dugong to passing vessels in previous reports. In this study, we will evaluate the effects of ship noises on dugongs' behavior. We obtained the underwater sound data set using an automatic under water sound monitoring systems for dugongs (AUSOMS-D) that were deployed in the southern part of Talibong Island, Trang, Thailand. We analyzed the data recorded from 10:00 on the 28th of February to 6:35 on the 4th of March 2005. Ship noise was detected with a detection software, which allowed a frequency range of 0.3 kHz through 1.0 kHz and a spectrum level of over 82 dB. We detected 71.1 ships (average) a day through the 117 consecutive recording hours. The most frequent boat traffic was observed between 15:00 to 15:30. The next logical step of this study is to draw moving trajectories of ships and dugongs, and also to examine the reactions of dugongs against each ship.