• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.2
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• pp.209-217
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• 2020

The purpose of this study was to compare the model-predicted and experimentally measured target strength (TS) of golden cuttlefish Sepia esculenta cuttlebones. Ultrasonic signals used to estimate frequency-dependent TS and the speed of sound in cuttlebones were measured by pulse-echo and through-transmission techniques, using a chirp sonar system and an ultrasonic pulser/receiver system under controlled laboratory conditions. The model appeared to slightly underestimate the predicted TS values in the frequency range of 100-160 kHz. However, there was good agreement between the predicted and measured TS values in the frequency range of 160-200 kHz. The significant similarity between the model-predicted and experimentally measured TS values supports the use of the Kirchhoff-ray mode (KRM) model for acoustic scattering analysis of cuttlebones. Accordingly, we concluded that the KRM model can be used as a tool to evaluate the frequency-dependent variability of TS due to changes in golden cuttlefish swimming depth.

• Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.361-367
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• 2014

Cuttlefish Sepia esculenta are commercially important in Korea. Assessments of their biomass currently depend on fishery-landings data, which may be biased. Towards fishery-independent acoustic surveys of cuttlefish, target strength (TS) measurements at 70 and 120 kHz were made of 23 live cuttlefish, in early May 2010. The fish were caught by traps in the inshore waters around Geojedo, Korea. The TS were measured using split-beam echosounders (Simrad ES60 and EY500, respectively). The cuttlefish mantle lengths (L) ranged from 15.6 to 23.5 cm (mean L=17.8 cm) and their masses (W) ranged from 335 to 1020 g (mean W=556.1 g). Their mean TS values at 70 and 120 kHz were -33.01 dB (std=1.39 dB) and -31.76 dB (std=2.15 dB), respectively. The mean TS at 70 kHz was 0.17 dB higher than the TS-length relationship resulting from a least-squares fit to the data ($TS=24.67{\log}_{10}L(cm)-64.03$, $r^2$ = 0.52, N=23). The mean TS at 120 kHz was 0.45 dB higher than the fitted TS-length relationship ($TS=40.59{\log}_{10}L(cm)-82.96$, $r^2$ = 0.58, N=23). The differences between the mean TS values and an equation regressed from all of the TS measurements at both frequencies ($TS=24.92{\log}_{10}L(cm)-4.92{\log}_{10}{\lambda}(m)-22.82$, $r^2$ = 0.86, N=46) was 0.22 dB at 70 kHz and 0.31 dB at 120 kHz, respectively.

• Fisheries and Aquatic Sciences
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• v.19 no.2
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• pp.8.1-8.11
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• 2016

To quantitatively estimate the influence of cuttlebone on the target strength (TS) of golden cuttlefish, the cuttlebone was carefully extracted from 19 live cuttlefish caught using traps in the inshore waters around Geojedo, Korea, in early May 2010 and the TS was measured using split-beam echosounders (Simrad ES60 and EY500). The TS-length relationships for the cuttlefish (before the extraction of cuttlebone, Fish Aquat Sci. 17:361-7, 2014) and the corresponding cuttlebone were compared. The cuttlebone length ($L_b$) ranged from 151 to 195 mm (mean $L_b$ = 168.3 mm) and the mass ($W_b$) ranged from 29.3 to 53.2 g (mean $W_b$ = 38.8 g). The mean TS values at 70 and 120 kHz were -33.60 dB (std = 1.12 dB) and -32.24 dB (std = 1.87 dB), respectively. The mean TS values of cuttlebone were 0.19 dB and 0.04 dB lower than those of cuttlefish at 70 and 120 kHz, respectively. For 70 and 120 kHz combined, the mean TS value of cuttlebone was -32.87 dB, 0.11 dB lower than that of cuttlefish (-32.76 dB). On the other hand, the mean TS value of cuttlebone predicted by the regression ($TS_b$ = 24.86 $log_{10}$ $L_b$ - 4.86 $log_{10}$ ${\lambda}$ - 22.58, $r^2$ = 0.85, N = 38, P < 0.01) was -33.10 dB, 0.04 dB lower than that of cuttlefish predicted by the regression ($TS_c$ = 24.62 $log_{10}$ $L_c$ - 4.62 $log_{10}$ ${\lambda}$ - 22.64, $r^2$ = 0.85, N = 38, P < 0.01). That is, the contribution of cuttlebone to the cuttlefish TS determined by the measured results was slightly greater than that by the predicted results. These results suggest that cuttlebone is responsible for the TS of cuttlefish, and the contribution is estimated to be at least 99 % of the total echo strength.