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. ======== 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
