
Estimation of target strength of Sardina pilchardus and Sardinella aurita by theoretical approachEstimation of target strength of Sardina pilchardus and Sardinella aurita by theoretical approach 
"/Ayoubi, Salaheddine El/"Ayoubi, Salaheddine El ,
"/Mamza, Kamal/"Mamza, Kamal ,
"/Fujino, Tadanori/"Fujino, Tadanori ,
"/Abe, Koki/"Abe, Koki ,
"/Amakasu, Kazuo/"Amakasu, Kazuo ,
"/Miyashita, Kazushi/"Miyashita, Kazushi
82
(
3
)
, pp.417

423 , 201605 , 日本水産学会
ISSN:09199268
Description
The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz were estimated by a prolatespheroid model, using measurements of swimbladder length and width. The ratio of swimbladder length to total length (TL) was similar in both species, however the ratio of swimbladder width to TL was smaller and more variable for S. aurita. Assuming a normal distribution of fish swimming orientation angle (θfish) with mean ± standard deviation (SD) of 0 ± 10°, the normalized (by TL) average TS (b20) was estimated to be 64.0 dB (38 kHz) and 65.2 dB (120 kHz) for S. pilchardus, and 66.2 dB (38 kHz) and 67.2 dB (120 kHz) for S. aurita. Compared with currently applied b20 values at 38 kHz, our results under four different θfish assumptions (0 ± 10°, 0 ± 15°, 5 ± 10°, and 5 ± 15°) were 69 dB higher for S. pilchardus and 57 dB higher for S. aurita. This suggests four to eightfold overestimation risk for S. pilchardus and three to fivefold overestimation risk for S. aurita when using the currently applied b20 values.
FullText
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