KARAKTERISTIK HAMBUR BALIK AKUSTIK PADA IKAN KAKAKTUA (Chlorurus sordidus) MELALUI PENGUKURAN SECARA EX-SITU DENGAN METODE AKUSTIK

Parrot fish (Chlorurus sordidus) is one of the herbivorous fish in coral reef ecosystems that has a role in maintaining the health of coral reefs. This study aims to study the characteristics of acoustic backscattering of parrot fish and their relationship to fish length measurements. The benefits of this study are useful for estimating the size and abundance distribution of parrot fish in a waters. Acoustic backscattering measurements were carried out ex-situ using the tethered method, where the parrot fish was hung at a depth of 2 meters below the transducer and sounded with a Simrad EK-15 echosounder at a frequency of 200 kHz. Recording data were analyzed with Echoview 8 software to obtain target strength (TS) data. The results showed that the backscatter of parrot fish (C. sordidus) had an average TS value of -49.42 dB at standard lengths ranging from 14 to 22 cm. Differences in TS values in parrot fish are thought to be influenced by body length, swimbladder length and swimming activity. The ratio of the size of the swimbladder length and body length does not indicate an association with TS values. The relationship between TS and standard length of parrot fish (C. sordidus) was formulated in the equation TS = 10.43 Log SL - 62.65 (R2 = 0.752). This result is different from the Love (1977) provision where the acoustic backscatter of a fish is the square of the length of the fish set with a slope (b) of 20.