• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.2
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• pp.137-146
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• 2012

Black porgy and fat greenling are commercially important fish species due to the continuously increasing demand in Korea. When estimating acoustically the fish length by a fish sizing echo sounder, it is of crucial importance to know the target strength (TS) to length dependence. In relation to these needs, the target strength experiments for live fishes were conducted in an acrylic salt water tank using two split-beam echo sounders operating at 70 and 120kHz. The target strength under well-controlled laboratory conditions was simultaneously measured with the swimming movement by digital video recording (DVR) system and analyzed as a function of fish length (L) and frequency (or wavelength ${\lambda}$). Equations of the form TS-alog (L)+blog (1)+c were derived for their TS-length dependence. The best fit regression of TS on fork length for black porgy was TS=20.62 log (L, m)-0.62 log (${\lambda}$, m)-30.68 ($r^2$=0.77). The best fit regression of TS on fork length for fat greenling was TS=12.06 log (L, m)-5.85 log (${\lambda}$, m)-22.15 ($r^2$=0.44).

• International Journal of Ocean System Engineering
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• v.3 no.3
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• pp.158-163
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• 2013

The acoustic target strength (TS) is one of the most important parameters for a submarine's stealth design. Because modem submarines are larger than their predecessors, TS must be managed at each design stage in order to reduce it. To predict the TS of a submarine, TASTRAN R1 was developed based on a Kirchhoff approximation in a high-frequency range. This program can present TS values that include multi-bounce effect in the exterior and interior of the structure by combining geometric optics (GO) and physical optics (PO) methods, anechoic coating effect by using the reflection coefficient, and response time pattern for a detected target. In this paper, TS calculations for a submarine model with the above effects are simulated by using this developed program, and the TS results are discussed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.4
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• pp.191-199
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• 1989

Research on the acoustic properties of fish has been carried out by a number of scientific workers from the earliest days of applying acoustic techniques to fish biomass estimates. This paper describes measurements of the target strength of Cyprinus Carpio, which measurements made at 50KHz in the experimental water tank. The results obtained are as follows: 1. The target strength(dB) of the fish has a directivity pattern quite similar to that of a transducer. The maximum value of target strength(dB) is obtained when the fish is insonified to its head-tail axis either from the dorsal or from the ventral side. 2. Empirical relationship between target strength(dB) and body length(cm) of the fish can be estimated as TS=20 Log L-65.4 where TS is the target strength of the fish and L is the body length of the fish. 3. The relationship between target strength(dB) and body weight(g) of the fish can be estimated as TS=6.7 Log W-53.7 where W is body weight of the fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.3
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• pp.248-256
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• 2010

Acoustic side-aspect target strength (TS) of living Japanese anchovy (Engraulis japonicus) was measured at 120kHz during in situ experiments. The data were collected by lowering and horizontally projecting the splitbeam transducer into the anchovy school. For analysis and interpretation of the side-aspect TS data, acoustic theoretical model, based on the fish morphology, and dorsal-aspect TS data were used. Total length of the anchovy ranged from 6.6 to 12.8cm (mean length 9.3cm). The side-aspect TS distributed between -40 and -55dB, has an obvious length dependency. The mean side-aspect TS of the anchovy was -47.8dB, and the TS was about 2dB higher than mean TS generated from dorsal-aspect measurements. With reference to maximum TS, the results of the side-aspect TS were distributed within the range of the theoretical and dorsal-aspect TS. Apparently these tendency indicates that side-aspect TS measured from the study is useful data. These in situ measurements of side-aspect TS can be applied to improve acoustic detection and estimates of the anchovy, and is necessary to measure with a various frequency and length for making enhance data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.442-445
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• 2004

The acoustic target strength (TS) of submarine is associated with its active detection, positioning and classification. That is, the survivability of submarine depends on its target strength. So it should be managed with all possible means. An anechoic coating to existing submarine or changing of curvature can be considered as major measures to reduce the TS of submarine. It is mainly based on the prediction of its TS. Under this circumstances, a study on the more accurate numerical methods becomes big topic for submarine design. In this paper, Kirchhoff approximation method was adopted as a numerical tool for the physical optics region. Secondly, the scaled models of submarine were built and tested in order to verify its performance. Through the comparison, it was found out that the Kirchhoff approximation method could be good design tool for the prediction of TS of submarine.

• 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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.427-434
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• 2014

Although ex situ target strength (TS) measurements using dual- and split-beam systems have become the primary approach of estimating fish abundance, theoretical model estimation is a powerful tool for verifying the measurements, as well as for providing values when making direct measurements is difficult. TS values for 20 samples of live bambooleaf wrasse (Pseudolabrus japonicus) whose target length (TL) ranged between 13.7 and 21.3 cm were estimated theoretically using the Kirchhoff-ray mode model, and the TS values for 18 live fish samples were additionally measured at ${\sim}0^{\circ}$ tilt angle to the swimming aspect using a tethered method at a frequency of 120 kHz to verify the theoretical values. The digitizing intervals used to extract the fish body and swim bladder morphology in the X-ray photographs significantly affected the calculated TS patterns, but variations based on the speed of sound and density ratio values for the general range of fish flesh were relatively small (within 1 dB). Close agreement was observed between the measured and theoretical TS values, and the correlation between the average TS and body length of the fish could be calculated accurately as <$TS_{120kHz}$>= 20logTL (cm) -71.6 using the theoretical method.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.239-248
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• 2003

This paper was conducted as an attempt in order to construct the data bank of target strength for acoustic estimation of fish length in the coastal waters of Korea. The fish length dependence of acoustic target strength for 13 large yellow croakers (Pseudosciaena crocea) at 75 kHz was investigated and the prediction of the target strength by using the Kirchhoff-Ray Mode model (KRM model) was compared with target strength measurements. The results obtained are summarized as follows; 1. In the averaged target strength pattern for 13 large yellow croakers the maximum target strength was -35.13 dB at $-13.35^{\circ}$ on a tilted angle. 2. The relationship between fork length(L, cm) and averaged target strength(TS, dB) was expressed as follows; TS=23. 76log (L) -73.45 (r=0.47) TS=20log(L) -67.35 From this result, the conversion coefficient was -73.45 dB and 6.1 dB lower than the coefficient -67.35 dB where the value of the slope of the regression equation is forced to be 20. 3. Averaged target strength and a length conversion coefficient derived from a target strength histogram for 13 large yellow croakers of mean length 25.59 cm were -41.23 dB, -69.72 dB, respectively. 4. In the range of $$2;{\ll} L (fish length /{\lambda}(wave length);{\ll}40$$, the prediction of the averaged target strength by the KRM model increased gradually with the increasing of $L/{\lambda}$ and was lower than the measured target strength.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.4
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• pp.265-275
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• 2005

A prerequisite for deriving the abundance estimates from acoustic surveys for commercially important fish species is the identification of target strength measurements for selected fish species. In relation to these needs, the goal of this study was to construct a data bank for converting the acoustic measurements of target strength to biological estimates of fish length and to simultaneously obtain the target strength-fish length relationship. Laboratory measurements of target strength on 15 commercially important fish species were carried out at five frequencies of 50, 70, 75, 120 and 200 kHz by single and split beam methods under the controlled conditions of the fresh and the sea water tanks with the 389 samples of dead and live fishes. The target strength pattern on individual fish of each species was measured as a function of tilt angle, ranging from $-45^{\circ}$ (head down aspect) to $+45^{\circ}$ (head up aspect) in $0.2^{\circ}$ intervals, and the averaged target strength was estimated by assuming the tilt angle distribution as N $(-5.0^{\circ},\;15.0^{\circ})$. The TS to fish length relationship for each species was independently derived by a least-squares fitting procedure. Also, a linear regression analysis for all species was performed to reduce the data to a set of empirical equations showing the variation of target strength to a fish length, wavelength and fish species. For four of the frequencies (50, 75, 120 and 200 kHz), an empirical model for fish target strength (TS, dB) averaged over the dorsal sapect of 602 fishes of 10 species and which spans the fish length (L, m) to wavelength (\Lambda,\;m)$ ratio between 5 and 73 was derived: $TS=19.44\;Log(L)+0.56\;Log(\Lambda)-30.9,\;(r^2=0.53)$.