Acoustic characteristics of a potentially important macroalgae, Sargassum horneri, for coastal fisheries

• Vesicles of Sargassum horneri tended to increase with increasing algal body weight. Contribution rate vesicles S. acoustic reflection was high. Target strength (TS) bodies increased Weight-dependent TS followed this equation: w = 11.1 log 10 W -71.1. Biomass can be estimated by measurements. A species macroalgae, , which has gas-filled vesicles, plays important roles as nursery grounds, feeding and hiding grounds for coastal fauna. In addition, it recently emerged a new fishery resource in Japan. However, its intensity is unknown, resulting the impossibility quantitatively estimating biomass via an survey quantitative echosounder. We measured target (dB re 1 m 2 ) clarified characteristics. The measurements were taken using 120 kHz echosounder fishing port Iwate Prefecture June July 2014. Seven samples collected scuba diving waters surrounding port. Each individual sample divided every 30 cm, each layer suspended at depth about 4–5 m, measured. Then, we into other parts. part exsiccated 80 °C over h. dry weights vesicle then weight ( Weight -71.1, R 0.81) considered that contribution gas high, similar swim bladder fish, strong what been reported bladder, owing accompanying Thus, could revealed our study.