Distribution of fish target strength value in Menjangan Island waters, West Bali National Park

¹ Marine Science and Technology Study Program, Faculty of Fisheries and Marine Science, Bogor 16680, Indonesia
² Department of Marine Science and Technology, Faculty of Fisheries and Marine Science, IPB University, Bogor 16680, Indonesia

^* Corresponding author: sripu@apps.ipb.ac.id

Abstract

Research on the target strength (TS) value of fish is generally influenced by various internal and external factors, either from fish or signals. This study aims to identify the composition and analyze the target strength value of fish in four directional zones in the waters of Menjangan Island. The distribution of fish TS values in 4 zones at depths of 1.5 - 5.0 m ranged from -59.8 to -39.5 dB. The presence of fish was validated by dive data, which showed that the composition of fish was dominated by the Pomacentridae family, at approximately 54.5%. Results from the estimation of fish length using Foote’s (1987) algorithm, ranged from 4.3 - 44.6 cm. Based on the zone, the North Zone had the highest number of fish detected at 2179 fish, while the West Zone had the lowest number at 1213 fish. The range of the TS values detected was dominated by the range of -61 to -58 dB and the least detected range was -40 to -37 dB. This indicates that the fish individuals detected around the depth near the surface of these waters tend to be small, and few were large, based on the results of the literature study.