Acoustic Target Strength Measurements for Biomass Estimation of Aquaculture Fish, Redlip Mullet (Chelon haematocheilus)

Hansoo Kim,Donhyug Kang,Mira Kim,Jisung Park,Sungho Cho,Kiseon Kim

doi:10.3390/app8091536

Abstract

Redlip mullet (Chelon haematocheilus) is distributed in coastal waters of the North-Western Pacific Ocean and is a cultured fish in Korea. A hydroacoustic technique constitutes a useful method to assess the biomass and spatial distribution of mullet in sea cages or in coastal waters, and acoustic target strength (TS) information of the target fish is an essential parameter in using this method. In this study, ex situ TS measurements of 16 live mullets were made in an aquaculture sea cage in Korea. The split-beam scientific echo-sounder used for measurements was comprised of 38, 120, 200, and 420 kHz frequencies. An underwater video camera was simultaneously used to observe the mullets’ behavior during the TS measurements. The mullet TS data was analyzed from a wide range of total fish length (FL: 14.3–40.3 cm). As results for all frequencies, the frequency dependence of the mean TS values were relatively low, and the difference in mean TS was within 2.5 dB. When the slope of the least-squares regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) at each frequency was −67.0 dB, −68.3 dB, −66.3 dB, and −68.5 dB, respectively. The data tended to be frequency dependent. Additionally, the maximum TS appeared between tilt angles of 0° and 10°. These results indicate that TS measurements can be applied to estimate the biomass of the mullet in sea cages or in coastal waters.

Highlights

Redlip mullet (Chelon haematocheilus) is a euryhaline species that inhabits both marine coastal water and freshwater environments [1,2]
The species is a commercial aquaculture fish in Korea and has an ecological niche in the marine ecosystem [2,3]. It is widely distributed around the coastal waters of Korea, Japan, Taiwan, and China in the North-Western Pacific Ocean [4]
The young mullet feeds on phytoplankton or small organic sediments in coastal waters and the adult mullet becomes omnivorous [5]

Summary

Introduction

Redlip mullet (Chelon haematocheilus) is a euryhaline species that inhabits both marine coastal water and freshwater environments [1,2]. The species is a commercial aquaculture fish in Korea and has an ecological niche in the marine ecosystem [2,3]. It is widely distributed around the coastal waters of Korea, Japan, Taiwan, and China in the North-Western Pacific Ocean [4]. The biomass of mullet in aquaculture nets has been estimated by the total wet weight (W) using a scale. As these methods are labor intensive and costly, it is necessary to consider more efficient methods. Since 2000, a hydroacoustic method using the acoustic equipment of fisheries has been implemented to estimate the distribution and abundance of fish in marine and freshwater

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Conclusion