Target Strength Values Research Articles

Corrigendum to: In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen

Triggerfish are widely distributed in tropical waters where they play an important ecological role. The black triggerfish Melichthys niger may be the dominant species around oceanic tropical islands, whereas pelagic triggerfish, such as the ocean triggerfish Canthidermis sufflamen, can assemble around fish aggregating devices (FADs) where they are a common bycatch of tuna fisheries. In this study we combined acoustic and optical recordings to provide the first in situ target strength (TS) measurement of black and ocean triggerfish. Data were collected in the Archipelago of Fernando de Noronha off north-east Brazil. The mean TS of a 27.8-cm-long black triggerfish at 70 and 200kHz was –39.3dB re 1m2 (CV=14.0%) and –38.9dB re 1m2 (CV=14.4%) respectively. The mean TS values of ocean triggerfish (with a size range of 39–44cm) at 70 and 200kHz were –36.0dB re 1m2 (CV=15.7%) and –33.3dB re 1m2 (CV=14.0%) respectively. This work opens up the field for acoustic biomass estimates. In addition, we have shown that TS values for ocean triggerfish are within the same range as those of small tunas. Therefore, acoustic data transmitted from FADs equipped with echosounders can introduce a bias in tuna acoustic biomass estimation and lead to increased rates of bycatch.

Comparison of Wideband vs Narrowband Acoustic Approach to Target Strength Value on Bullet Tuna (Auxis rochei) and Bonito (Euthynnus affinis)

Target strength (TS) is one of the main parameters for determining fish density, abundance and biomass in acoustic technique. Therefore, it is of utmost importance to obtain an accurate TS estimate and to minimize bias from its measurement. Various factors contribute to bias in acoustic TS, namely the high diversity of species, body shape, size and also frequencies used. In this paper we compare and examine the acoustic narrowband (NB) and wideband (WB) approaches to better understand the TS response to various frequencies. The use of acoustic wideband approach, is expected to perform better and be less-biased than the narrowband, which is still widely used. The measurement of bullet tuna (Auxis rochei) and bonito (Euthynnus affinis) for the same fork length (FL) size showed the power of four frequency dependent (f^4). Furthermore, a comparison between NB frequency of 200 kHz versus WB at the nearby frequencies of 190-200 kHz and 200-210 kHz showed a significant Pearson correlation value for bonito fish size range from 17-26.6 cm, whereas in the case of bullet tuna, fish had no significant correlation at alpha=0.05 for fish size range from 16.4-26 cm.

The strength oriented mix design for geopolymer concrete using Taguchi method and Indian concrete mix design code

This paper represents the mix design of geopolymer concrete based on the target strength criteria by optimizing the proportions of the constituents using Taguchi method. The guidelines of IS:10262–2019 were followed for the mix design. The GPC contains a broader range of constituents. Therefore, numerous trial mixes are required to obtain the mix for the best strength of the GPC mix. Moreover, the conventional mix design of GPC does not target the strength. In this study, the mix design based on the strength criterion is proposed and optimized by the Taguchi method, considering all primary constituents and their proportions. The tests for workability, compressive strength, and splitting tensile strength were included. The test results showed excellent agreement with the target strength values. The study encouraged the development of the strength-based mix design of GPC as per the code and optimized by the Taguchi method, avoiding enormous trials and approximations for the mix design of GPC.

Verification of the Backscattering Strength Based on the Swimming Behavior of Antarctic Krill

This study provides an estimate of the SDWBA-modelled mean target strength for given sets of krill length and swimming orientation. The range of the dB identification window for krill length was between 28 mm and 67 mm and the distribution of swimming orientation N[11.0°, 4.0°] was estimated to be between 0.06–10.97 dB, while the range estimated using N[53.1°, 21.4°], i.e., the distribution of orientation obtained under the brightest illuminance level, was 5.21–9.82 dB. The range of the dB window calculated using N[45.2°, 23.0°], obtained under the second brightest illuminance level, was 3.83–11.76 dB, and the range calculated with N[48.1°, 23.0°], obtained under the third illuminance level, was 3.83–11.76 dB. The range of the dB window calculated by N[45.9°, 23.0°] was 3.41–11.75 dB, and the range of the dB window for krill length ranging from 28 mm to 67 mm was 4.05–11.34 dB. In all the swimming orientations, the smaller the krill size was the lower the averaged target strength value was; likewise, the larger the krill size was the higher the averaged target strength value was. The result indicated that swimming orientation impacted greatly on the range of frequency differences of Antarctic krill.

Hydroacoustic target strength vs. fish length revisited: Data of caged, free-swimming European whitefish (Coregonus lavaretus L.) suggest a bi-phasic linear relationship under a limited range of tilt angles

To develop specific target strength (TS) - fish length relationships using 38 kHz and 120 kHz split beam echosounders, we measured TS (dB) in five size groups (5−59 cm total length) of European whitefish (Coregonus lavaretus) swimming freely in a net cage of 4 m diameter and 8 m height. For 120 kHz, we deployed down-looking (dorsal aspect) as well as upwards-looking (ventral aspect) transducers, whereas 38 kHz measurements were taken for the dorsal aspect only. The ventral aspect dataset revealed stronger TS values especially for the larger length classes. The dorsal aspect datasets of both frequencies were not significantly different across all lengths and both showed a steep increase of the relationship in small sizes (5−20 cm) which levelled off in the larger sizes (>20 cm). For 120 kHz the slope of a linear regression of TS vs. log fish length was 29.8 for fish between 5−20 cm (much higher than the generally proposed slope of 20), while in fish >20 cm the slope was 10.7 which is far below the generally proposed value. We advocate considering a potential bi-phasic linear regression of the log length – TS relationship for all species whenever a large size range of fish is studied, encompassing significant proportions below and above approximately 20 cm total length.

Indonesian short fin eel Anguilla bicolor (Mclelland, 1844) swim bladder as important organ for reflecting acoustic wave

Indonesian shortfin eel, Anguilla bicolor (McClelland, 1844) is one of fish that have swim bladder to assist swim and doing migration. Every fish has different shape, gas volume, dimension, and length ratio of swim bladder, which can play role in the difference in backscattering of acoustic energy. This study aims to determine the shape, dimensions and ratio of Anguilla bicolor’s swim bladder and their effect on target strength (TS) values. The research was conducted in two places, in the Acoustic lab, Department of Marine Science and Technology, Bogor University and Laboratory of Histology and Embryology, Faculty of Biology, Universitas Gadjah Mada. Retrieving data using the EK-15, Frequency 200 KHz tool and also the X-ray photo. The results show the shape of the swim bladder of Anguilla bicolor is elongated and consists of 1 room which is generally called a closed swim bladder. Acoustic detection results show that fish with large swim bladder volumes have large TS values and conversely fish with small swim bladder volumes have a small TS value.

In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen

Triggerfish are widely distributed in tropical waters where they play an important ecological role. The black triggerfish Melichthys niger may be the dominant species around oceanic tropical islands, whereas pelagic triggerfish, such as the ocean triggerfish Canthidermis sufflamen, can assemble around fish aggregating devices (FADs) where they are a common bycatch of tuna fisheries. In this study we combined acoustic and optical recordings to provide the first in situ target strength (TS) measurement of black and ocean triggerfish. Data were collected in the Archipelago of Fernando de Noronha off north-east Brazil. The mean TS of a 27.8-cm-long black triggerfish at 70 and 200kHz was –39.3dB re 1m2 (CV=14.0%) and –38.9dB re 1m2 (CV=14.4%) respectively. The mean TS values of ocean triggerfish (with a size range of 39–44cm) at 70 and 200kHz were –36.0dB re 1m2 (CV=15.7%) and –33.3dB re 1m2 (CV=14.0%) respectively. This work opens up the field for acoustic biomass estimates. In addition, we have shown that TS values for ocean triggerfish are within the same range as those of small tunas. Therefore, acoustic data transmitted from FADs equipped with echosounders can introduce a bias in tuna acoustic biomass estimation and lead to increased rates of bycatch.

Monitoring of biomass at Cooling Water System of hongyanhe nuclear power plant by using acoustic methods

In recent years, there have been large-scale jellyfish outbreaks in the Bohai Sea in summer, which have greatly affected the water intake for cold source of Hongyanhe nuclear power station in Fuzhou bay and threatened the normal operation. This study aims at early warning of invasion of jellyfish, designs and develops acoustic monitoring system for cold source biological (jellyfish)by using ascientificechosounder (EY60,70kHz,Simrad), and carries out real-time monitoring of the echo of cold source biological entering water intake, so as to obtain the resource density of jellyfish from June to September 2019. The acoustic data is processed with a software of Echoview to calculate the average SV and detect the strength of the single target to calculate the daily average flux of the monitoring point. According to the monitoring results, the maximum and minimum daily average values of SV were -62.7dB and -80.0dB, respectively. The maximum and minimum daily average values of target strength are -37.2dB and -81.0dB, respectively. The maximum and minimum daily average values of flux are 5.36ind/(s•m2) and 1.2x10-5ind/(s•m2).Combined with the daily cleaning amount of the monitoring point back-end intercepting network and meteorological data, the comparative analysis is carried out to determine the index level of the acoustic warning for cold source biological flowing into the water intake according to the correlation between average flux and amount of cleaned net.

In situ target strength of bigeye tuna (Thunnus obesus) associated with fish aggregating devices

Abstract Bigeye tuna (Thunnus obesus) is an important commercial fish species, which aggregates around fish aggregating devices (FADs) together with other tropical tuna species. Acoustics is the main technology used by fishers and scientists for the location and quantification of tunas at FADs. However, currently it is not possible to reliably discriminate between the different tropical tuna species that are found together at FADs using acoustic methods, which hampers the development of selective fishing needed to preserve some of the tropical tuna species for which overfishing is occurring. One of the prerequisites for species discrimination is to know the target strength (TS) of each species at different frequencies. This paper measures in situ TS values and explores the frequency response of bigeye tuna at FADs in the central Pacific Ocean using three different acoustic frequencies. For the range of body length caught (40–100 cm), the obtained b20 values were −65, −66, and −72 dB for 38, 120, and 200 kHz, respectively. The decreasing frequency response pattern obtained for this swimbladder bearing species contrasts with the opposite pattern previously observed for skipjack tuna (bladder-less), the most abundant tuna species found at FADs, hence allowing the potential for discrimination between the two species.

Measurement and analysis of TS-Frequency relationship on mackerel tuna (Euthynnus affinis) using bandwidth frequency

Mackerel tuna (Euthynnus affinis) is a pelagic fish from Scombridae family and one of the commercially important species. The fish is mostly found in the water column from the surface down to about 50 m. Mackerel tuna spread widely in the tropical and subtropical waters, including the Indian Ocean, Pacific, Mediterranean Sea, and Black Sea. Since the level of exploitation of this fish resource is relatively high, it is critical to have an accurate assessment on the status of the stock. In this paper we report and discuss the measurement results of the acoustic target strength (TS) of Mackerel tuna using acoustic broadband technique. A broadband technique was used to better characterized the basic TS-Frequency relationship of the target, and hence less bias in biomass estimation. Target Strength measurement was performed using SIMRAD EK-80 scientific acoustic instrument with frequency bandwidth 160-240 kHz and sound pulse was transmitted to the target with 1 CW pulse and 8 FM pulse. The fish was tethered and positioned directly below the acoustic transducer. The results of the measurements are presented in terms of TS-Frequency. It is found that the TS-F relationship fluctuates, where the highest TS value -54.64 ± 4.64 dB is in 190-200 kHz frequency interval.

Bioacoustic application on fisheries management in an artificial reefs’ ecological reserve of Bohai Gulf China

Various techniques have been used in marine fishery resources assessment. Among those, acoustic techniques have high efficiency and wide adaptability, and are environment friendly. Therefore, acoustic techniques played a key/indispensable role in the field of ecosystem-based fishery management. Acoustic surveys were conducted during the wet (May) and dry (November) seasons in 2016 in the artificial reefs ecological reserve of Bohai Gulf and a nearby control region to understand the current situation of fishery resources and explore the effectiveness of underwater artificial constructions by a dual-frequency identification sonar (DIDSON) and a scientific split-beam echosounder (120 KHz, Simrad EY60). Fish densities in various seasons and regions showed significant differences and interaction, with a maximum value of 358020.34 ind/n.mile2 in the artificial reefs’ region and a minimum value of 71898.35 ind/n.mile2 in the control region during the wet season. Fish densities in defined parallel transects revealed a roughly southward migration trend of small-size individuals from wet season to dry season. Single echo detections in the artificial reefs region demonstrated a wider target strength (TS) range (− 60 ~ − 30 dB vs − 60 ~ − 51 dB) and higher mean TS values (− 55.87 dB vs − 58.31 dB) than the control region both in the wet and dry seasons, which indicated a more complicated and stable fish community structure in the artificial reefs area. The vertical distribution of single echo detections tracked by the echoview post-processing system showed an apparent downward gathering effect. A positive correlation between TS and water depth was discovered from Pearson correlation analysis in the artificial reefs region during the dry season.

Acoustic Target Strength Measurements for Biomass Estimation of Aquaculture Fish, Redlip Mullet (Chelon haematocheilus)

Redlip mullet (Chelon haematocheilus) is distributed in coastal waters of the North-Western Pacific Ocean and is a cultured fish in Korea. A hydroacoustic technique constitutes a useful method to assess the biomass and spatial distribution of mullet in sea cages or in coastal waters, and acoustic target strength (TS) information of the target fish is an essential parameter in using this method. In this study, ex situ TS measurements of 16 live mullets were made in an aquaculture sea cage in Korea. The split-beam scientific echo-sounder used for measurements was comprised of 38, 120, 200, and 420 kHz frequencies. An underwater video camera was simultaneously used to observe the mullets’ behavior during the TS measurements. The mullet TS data was analyzed from a wide range of total fish length (FL: 14.3–40.3 cm). As results for all frequencies, the frequency dependence of the mean TS values were relatively low, and the difference in mean TS was within 2.5 dB. When the slope of the least-squares regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) at each frequency was −67.0 dB, −68.3 dB, −66.3 dB, and −68.5 dB, respectively. The data tended to be frequency dependent. Additionally, the maximum TS appeared between tilt angles of 0° and 10°. These results indicate that TS measurements can be applied to estimate the biomass of the mullet in sea cages or in coastal waters.

Seahorse Acoustic Reflection on Active and Passive Moving Condition : A Prelyminary Observation in Watertank

Identification and estimation of seahorse population in the marine environment are difficult to obtain. Nowadays, the observations use visual techniques, biologic and statistics. Bio-statistics approach has some limitations, such as times consuming and low accuracy. An approach was required to provide more accurate information, comprehensive, and based on telemetry (underwater acoustic). Acoustic reflection is an important information to observe underwater objects that can be used for stock assessment and behavioral studies. This research is a preliminary observation and measurement of seahorse Target Strength (TS). The results show that there are differences in TS value of seahorse at the active and passive moving condition. The fluctuations of TS values in active conditions are higher than those in passive conditions. This study has also found that the average TS value of seahorse in active moving conditions is -54.49 dB (± 3 dB). It is greater than the mean TS value in passive moving conditions -59.64 dB (± 3 dB). The approach of immobile fish (the passive moving condition) on the seahorse is better to increase the correlation value between TS to size. The relationship between TS and the size of the seahorse are discussed in the results of this study

Target-strength Measurements of Sandfish Arctoscopus japonicus

The goal of this study was to estimate the target strength (TS) of the sandfish Arctoscopus japonicus using in-situ and ex-situ methods with an echosounder. For the in-situ TS measurement, the survey was conducted by taking hydroacoustic measurements at 38 and 120 kHz and using a coastal gill net, in Goseong, in the northeastern sea of Korea in early December 2009. Ex-situ measurement of TS used live specimens and the tethering method, and was conducted at 120 kHz. The distribution of fork length (FL) was bimodal: 14.6–19.8 cm (n = 241 individuals, mean = 17.0 cm) for males and 16.3–24.5 cm (n = 105 individuals, mean = 19.6 cm) for females. The in-situ TS ranged from −79.8 to −59.1 dB (mean = −74.3 dB for males and −64.1 dB for females) at 38 kHz and −79.9 to −56.2 dB (mean = −74.3 dB for males and −64.1 dB for females) at 120 kHz. The mean TS of females was approximately 10 dB higher than that of males at each dominant frequency. The female ex-situ TS values ranged from 68.5 to −54.6 dB, and those of males was from −67.7 to −59.3 dB. The mean TS value for females was 2.9 dB higher than that of males. These results may be used in echo-integration surveys of sandfish to estimate their abundance and seasonal distribution.

Behavioral patterns and in-situ target strength of the hairtail (Trichiurus lepturus) via coupling of scientific echosounder and acoustic camera data

The present study focuses on the influence of target strength (TS) changes in the swimming angle of the hairtail (Trichiurus lepturus). We measured in-situ TS at 38 and 120 kHz with luring lamps at a fishing ground for jigging boats near the coastal waters of Jeju-do in Korea. Swimming angle and size of hairtails were measured using an acoustic camera. Results showed that mean preanal length was estimated to be 13.5 cm (SD = 2.7 cm) and mean swimming tilt angle was estimated to be 43.9° (SD = 17.6°). The mean TS values were −35.7 and −41.2 dB at 38 and 120 kHz, respectively. The results will assist in understanding the influence of swimming angle on the TS of hairtails and, thus, improve the accuracy of biomass estimates.

Evaluating the performance of very weak subgrade soils treated/stabilized with cementitious materials for sustainable pavements

Abstract This paper presents the results of laboratory tests that were conducted to determine the proper treatment/stabilization recipe of very weak subgrade soils at high moisture contents, and to evaluate the corresponding performance-related properties [e.g., the resilient modulus and permanent deformation] for use in the design of sustainable pavement structures. Four different subgrade soil types of different plasticity indices were considered in this study. Three different moisture contents were selected at the wet-side of optimum that correspond to a raw soil strength value of 172 kPa (25 psi) or less. All the soils were treated with different combinations of class C fly ash (or Portland cement type I) and hydrated lime to achieve a 7-day target strength values of 345 kPa (50 psi) to create a working platform and 690 kPa (100 psi) to stabilize the subgrade for subbase application. Repeated load triaxial (RLT) tests were performed on laboratory molded specimens to evaluate their resilient modulus and permanent deformation behavior under cyclic loading. The AASHTO T-307 procedure was followed in this study to conduct the resilient modulus tests. A good correlation was observed between the water/additive ratio and the resilient modulus/permanent deformation, such that the soil specimens prepared at low water/additive ratio showed better performance than those prepared at high water/additive ratio. The results of laboratory tests showed that the use of direct correlation between unconfined compressive strength (UCS) and resilient modulus for cementitiously treated/stabilized soils can be misleading.

Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): the nighttime scattering layer

Engraulis anchoita is a physostomous fish with a dual chambered swimbladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse forming a scattering layer near the sea surface. A survey data series comprising more than 50000 single target detections, recorded from 1995 to 2008, was analyzed in order to study the species specific TS at 38 kHz. A TS vs. fish total length (L) equation was obtained from the in situ measurements (TS = 31.9 log L – 82.4 dB; r2= 0.78). When the slope of the regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) was −68.6 dB. In any case, these results indicate an average difference of +3 dB (higher TS values) when compared with the general model suggested for clupeoid fish. The TS measurements obtained inside the nighttime sound scattering layer exhibited a negative trend with depth. An empirical depth dependence term for the anchovy TS equation was obtained through a three parameter least square fitting of the data [TS = 31.3 log L – 79.6 dB – 4.74 log (1 + z/10); r2 = 0.74]. Anatomical data obtained through high resolution X-Ray Computed Tomography was employed as input for a Prolate Spheroidal Model (PSM). Theoretical TS vs. tilt angle functions were obtained considering the compression of the sb at different depths and under the assumption of different contraction rates. The TS functions were then averaged over different fish tilt angle distributions and used to derive theoretical depth dependence curves of average fish TS. The implications of the adopted sb contraction rate and tilt angle distribution are discussed by comparing the modelled TS(z) curves against the empirical data.

Creep modeling of concretes with high volumes of supplementary cementitious materials and its application to concrete-filled tubes

The use of concretes with supplementary cementitious materials (SCM concretes) is a mechanism to improve the sustainability of structural systems. However, most reinforced concrete (including cast-in-place and precast) structural components rely on early stiffness and strength of the concrete to resist self-weight and construction loadings after release of the formwork. In contrast to cement-only concretes, SCM concretes require more time to reach the target strength and stiffness values and therefore a structural component that does not depend on these engineering properties during construction is required. Use of concrete-filled tubes (CFTs) is a solution. With a CFT, the steel tube is able to support construction loads while the high SCM concrete fill develops its strength and stiffness. However, there are concerns about load transfer (from the concrete to the steel tube) during the development of these properties and the long-term deformations (creep) of high SCM concrete and its impact on CFT performance. This research develops models to predict the long-term (creep) response of SCM concretes and uses those predictive models to assess the long-term response of CFTs with SCM concrete fill. Three time-dependent models were developed: compressive strength, elastic modulus, and creep. The models were validated using a large SCM database and two full-scale CFTs with SCM concrete fill that were tested under sustained loading. Once verified, a parametric study was conducted. The results indicate that SCM concretes with binder ratios (total ratio of CaO/(SiO2 + Al2O3) in all binders—cement and SCMs) greater than 0.5 behaved similarly to CFTs with cement-only concrete fill.

Size estimation of walleye pollack (Theragra chalcogramma) by using a broadband split-beam system

Recently, broadband quantitative echo sounders have been developed. These systems can measure single echo traces from individual fish with high range resolution. They can be used for the accurate size distribution by measuring the target strength. On the other hand, walleye pollack is one of the important species for stuck management in Japan. They form a school at juvenile stage. We compared the captured fish size using bottom trawl net with the acoustically estimated values. We conducted the survey in July 2015 in east side of off Hokkaido, Japan, using the fisheries research vessel Kaiyo-maru No. 5 (495 tons), which is equipped with narrowband echo sounder transducers (EK-60, Kongsberg, 38, 70, 120, and 200 kHz). The broadband split-beam transducer (FSS-SBX, Furuno) was deployed at the ship sideboard. All of the clock of the system were synchronized for comparison of data. More single echo traces could be measured using the broadband system than those measured by the narrowband system. Fork lengths were estimated at 3~70 cm based on the maximum normalized target strength value: -60 dB. We confirmed that good agreement of size distribution between catch and acoustic estimation. The broadband systems may be helpful tool for estimating body size of fish.

Accuracy verification of tilt-angle estimation by split-beam echosounder: Comparison with acceleration data-logger data

Fish tilt-angle is one of the most important factors for fish target strength (TS) estimation, because the little change varies TS value dramatically. Split-beam echosounder collects a fish position with 3-D coordinates. Hence, if fish swim within acoustic beam continuously, the tilt-angle can be estimated from the gap between two positions easily. However, the accuracy of the estimation depends on performance of the echosounder. We verified accuracy of the estimated tilt-angle by comparing high-resolution angle from an acceleration data logger. Experiment was conducted at a large experimental tank (W:10m x D:5m x H:6m) in HRCFO. A 2-axis acceleration data logger (φ15 mm, L: 53 mm, M190L-D2GT, Little Leonardo, Inc.) was tethered into the tank, and towed at respective angle from -50 to 50 degree (1 degree pitch). Positions of the logger echos (from KCE300, Sonic Co., 120kHz) were exported by algorithms of Echoview7.1. After this process, the tilt-angles were calculated. 28 logger echos were identified from the acoustic data, and the estimated tilt-angles was from -45.59° to 32.87 °. Significant correlation of tilt-angles (logger vs. acoustic data) was found (p > 0.01, r2 = 0.90). This result shows high precision of the estimated tile angle from the split-beam echosounder data.