| Summary: | 碩士 === 國立中山大學 === 海下技術研究所 === 92 === There are many Sciaenid species found in coastal water of Taiwan, and most of them can generate sound in the spawning season. However due to overfishing, the populations of these high economic value fishes have been greatly decreased. To study and protect Sciaenid, whose habitat should be identified to set up seasonal protection zones. In this study, easy and low cost measure by using passive sonar is proposed to map the habitat in the field. Measurement and analysis of Sciaenid’s sound were performed to investigate its acoustic characteristic, and frequency range was found to be 350 to 1,500 Hz. The statistical distribution of sound levels can be built up by enough field measurement, therefore source levels can be defined in this method. In the addition, the transmission loss of in site shallow water was studied to compute the real decaying factor (TL=n*logR) of the survey site. By using 3 sonobuoys, with known source level distribution and transmission loss, the distance of possible habitat can then be inverted. Through enough measurements, the map of coastal habitat of Sciaenid can be generated with efficiency and accuracy.
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