In Fisheries Science, Vol. 70(5), October 2004, I found
the following article:
Donhyug KANG, Kazuhiro SADAYASU, Tohru MUKAI, Kohji IIDA, Doojin HWANG,
Kouichi SAWADA, Kazushi MIYASHITA (2004): Target strength estimation of
black porgy Acanthopagrus schlegeli using acoustic measurements and a
scattering model. Fisheries Science, Vol. 70(5), 819-828.
Abstract: Black porgy are hatched and released in marine ranching areas in
Japan, Korea and Taiwan to maintain fisheries resources in coastal areas. If
acoustic methods are used for field surveys, target strength (TS)
information on the species is needed to convert acoustic data to biomass
density. Target strength of black porgy (Acanthopagrus schlegeli) 15.5-32.9
cm fork length (nine individuals) was measured at 38 and 120 kHz (split
beam) by ex situ measurements (cage and fishhook methods) of living fish, a
tethered method with shock-frozen fish, and an acoustic scattering model,
the Kirchhoff ray mode (KRM) model based on fish morphology. The ex situ
TS-to-fork length (FL, cm) relationships were TS38kHz = 20log10FL 64.6 (r =
0.77) and TS120kHz = 20log10FL 65.2 (r = 0.70). The values for the KRM
model were TS38kHz = 20log10FL 64.8 (r = 0.88) and TS120kHz = 20log10FL
65.4 (r = 0.80). The agreement between the ex situ measurements and the KRM
model for the mean TS was very good. In contrast, the results for the
tethered method (TS38kHz = 20log10FL 69.3 [r = 0.42]) differed markedly
from the other two methods, perhaps because of the effects of the
shock-freezing procedure in air. The results of the ex situ measurements and
scattering model provide basic information for studying TS and conducting
acoustic surveys of black porgy, even though the tethered method must be
modified.
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Sonja Amoser
PhD Student, Research Associate University of Vienna, Institute of Zoology
Althanstrasse 14, 1090 Vienna, Austria
[EMAIL PROTECTED]
tel: +43 (1) 4277 54467
fax: +43 (1) 4277 54406
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