Target Strength of Sargassom

Communities of seaweeds are greatly important fields for coastal fisheries in Japan.since some kinds of fishes feed and grow around or in them.A series of echo measurements at frequencies of 50 and ZOOkHz was made on target strength of 20 samples, 7 species of sargassoms in 1385.A bunch of target sargassom was made to have a diameter within the pulse length emitted from an echosounder.The sargassoms give relatively strong echoes due to their gas-filled vesicles as compared with a kelp with no vesicles.Nhole vesicles of each sample are measured with a micrometer for their lengths of minor.¢s and major axes.d...An equivalent radius.Re of the vesicle is:where, t is a thickness of a vesicle shell.Experimental formulae.t= a Re +h, for thickness.t. measured by species are given for estimating respective thickness of a given Re.The calculated target strength.TSc is: rsc = 10 log (hush/4) rsc of the sargassoms agrees with observed TS.This fact may prove Urick's hypothesis on Sv.