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Koki ABE

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Papers by Koki ABE

Estimation of target strength of Sardina pilchardus and Sardinella aurita by theoretical approach

Fisheries Science, 2016

The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz w... more The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz were estimated by a prolate-spheroid 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 6-9 dB higher for S. pilchardus and 5-7 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.

Tilt Angle and Theoretical Target Strength of the Japanese Sandeel, Ammodytes personatus, Captured on the Northern Coast of Hokkaido

The Journal of the Marine Acoustics Society of Japan, 2013

The tilt angle, i.e., the angle from horizontal made by the fish body as its head dives down or u... more The tilt angle, i.e., the angle from horizontal made by the fish body as its head dives down or up, affects the readings on fish echo soundings. We measured the tilt angle of Japanese sandeels (Ammodytes personatus Girard) in a water tank, and calculated the acoustic target strength (TS) using a theoretical scattering model. This study examined the TS of sandeels from the northern coast of Hokkaido, which have a larger body size than those in other regions in Japan. TS values for sandeels, a swimbladderless fish, were estimated using a distorted-wave Born approximation (DWBA) model at two frequencies: 38 and 120 kHz. The mean tilt angle was 20.4° (S.D.=18.5°), which differed slightly from that of the lesser sandeel, Ammodytes marinus. The regression equations of the average TS values were TS 38 kHz =8.2 log 10 SL-74.2 and TS 120 kHz =20.9 log 10 SL-92.6, respectively. At 120 kHz, the slope was close to 20, suggesting that the acoustic backscattering strength was proportional to the square of the body length. This value was smaller at 38 kHz, suggesting that the acoustic backscattering strength was stable to differences in body length. We obtained a small discrepancy for both frequencies (ΔTS=TS 120 kHz -TS 38 kHz ) were TS 120 kHz <TS 38 kHz . Discrepancies of -1.3 dB for the maximum TS, and -1.8 dB for averaged TS were found in 72 fish samples, which would be useful for identifying sandeel schools in practical analysis using TS differences.

Measurements of Sound-Speed in the Tissue of Juvenile Southern Bluefin Tuna (Thunnus maccoyii) for Target Strength Estimation

The Journal of the Marine Acoustics Society of Japan, 2007

＊ 2 Kozo TOKUYAMA (FURUNO Electoric Co.) ターゲットストレングス推定に必要なミナミマグロ (Thunnus maccoyii) 幼魚の魚肉内音速測定 ... more

A Connection Model between the Positioning Mechanism and Ultrasonic Measurement System via a Web Browser to Assess Acoustic Target Strength

SICE Journal of Control, Measurement, and System Integration, 2009

This paper details a network-controlled measurement system for use in fisheries engineering. The ... more This paper details a network-controlled measurement system for use in fisheries engineering. The target strength (TS) of fish is important in order to convert acoustic integration values obtained during acoustic surveys into estimates of fish abundance. The target strength pattern is measured with the combination of the rotation system for the aspect of the sample and the echo data acquisition system using the underwater supersonic wave. The user interface of the network architecture is designed for collaborative use with researchers in other organizations. The flexible network architecture is based on the web direct-access model for the rotation mechanism. The user interface is available for monitoring and controlling via a web browser that is installed in any terminal PC (personal computer). Previously the combination of two applications was performed not by a web browser but by the exclusive interface program. So a connection model is proposed between two applications by indirect communication via the DCOM (Distributed Component Object Model) server and added in the web direct-access model. A prompt report system in the TS measurement system and a positioning and measurement system using an electric flatcar via a web browser are developed. By a secure network architecture, DCOM communications via both Intranet and LAN are successfully certificated.

Application of broadband dolphin mimetic sonar for discriminating target fish species

For the acoustic species discrimination, broadband response of three tuna species, bigeye tuna, y... more For the acoustic species discrimination, broadband response of three tuna species, bigeye tuna, yellowfin tuna and skipjack tuna were measured by a broadband split beam sonar system. Each species was kept in an enclosure separately. Ultrasonic broadband sound (70 kHz -140kHz) was projected nearly horizontally to the captive fish body in a floating pen. Three major echoes were detected from each fish. The delay time between earlier and last echo corresponded to the body width of the target fish. These echoes seemed to come from the left and right body surface of each fish when the acoustic beam projected transversally to the fish body. The dominant echo at the middle between body surface echoes was considered to come from the center of the body such as the swimbladder and/or the spine. As already known, bigeye tuna has swimbladder where as skipjack tuna does not. Yellowfin tuna has smaller swimblader than that of bigeye tuna. The relative intensity of the body surface echo to the body center echo was large for skipjack tuna and small for bigeye tuna. This is consistent with the large target strength of the swimbladder rather than the spine or other unidentified reflectors in the body center of the fish. This could be a key for the species discrimination. More sample size and experiment including numerical simulation is needed as the future research.

Development of an acoustic-optical system to estimate target-strengths and tilt angles from fish aggregations

Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600)

The J-QUEST instrument package, a quantitative 70kHz split-beam echo sounder and a stereo TV came... more The J-QUEST instrument package, a quantitative 70kHz split-beam echo sounder and a stereo TV camera, is being developed to observe mesopelagic fish. In situ acoustic and optical measurements of single fish within aggregations include swimming speed, target strength, length, and tilt angle. Acoustic data and two video signals are monitored in real-time via an optical-power composite cable and receivers on deck. The J-QUEST was deployed from the R/V Kaiyo-maru in the transient waters of the Kuroshio current from Kashima-nada to off the coast of Sanriku in the east of Japan. J-QUEST was tethered from the surface to a depth of 200m and worked well. In Kashima-nada at a depth of 10m, Pacific saury (Cololabis saira) were attracted to the underwater lights and formed a large aggregation around J-QUEST. We could monitor fish on both the TV monitors and on the echogram. Average target strength of Pacific saury was -37.9dB and normalized TS (by squared fork length) was -66.8dB.

Swimbladders under pressure: anatomical and acoustic responses by walleye pollock

ICES Journal of Marine Science, 2009

Horne, J. K., Sawada, K., Abe, K., Kreisberg, R. B., Barbee, D. H., and Sadayasu, K. 2009. Swimbl... more Horne, J. K., Sawada, K., Abe, K., Kreisberg, R. B., Barbee, D. H., and Sadayasu, K. 2009. Swimbladders under pressure: anatomical and acoustic responses by walleye pollock. – ICES Journal of Marine Science, 66: 1162–1168. Pressure influences echo intensities from fish through changes in swimbladder volumes and surface areas. Volume reduction is expected to correspond to Boyle’s law (volume α pressure−1), but the effects of deforming the dorsal-aspect surface area of the swimbladder on the target strength (TS) of a physoclist have not been quantified at geometric scattering frequencies. Dorsal and lateral radiographs of three juvenile walleye pollock (Theragra chalcogramma) in a pressure chamber were used to image swimbladders from ambient to a maximum of 4.9 × 105 Pa (i.e. 5 atm). Radiographs from an additional 16 0-group, 21 juvenile, and 28 adult fish were used to compare swimbladder sizes and shapes across life-history stages. The directional elliptical eccentricity, which descr...

Target-strength, length, and tilt-angle measurements of Pacific saury (Cololabis saira) and Japanese anchovy (Engraulis japonicus) using an acoustic-optical system

ICES Journal of Marine Science, 2009

Sawada, K., Takahashi, H., Abe, K., Ichii, T., Watanabe, K., and Takao, Y. 2009. Target-strength,... more Sawada, K., Takahashi, H., Abe, K., Ichii, T., Watanabe, K., and Takao, Y. 2009. Target-strength, length, and tilt-angle measurements of Pacific saury (Cololabis saira) and Japanese anchovy (Engraulis japonicus) using an acoustic-optical system. – ICES Journal of Marine Science, 66: 1212–1218. Pacific saury and Japanese anchovy generally congregate in dense groups or schools. An acoustic-optical system (the Japanese Quantitative Echosounder and Stereo-video Camera System or J-QUEST) has been developed to measure accurately the target strength (TS) of fish in a dense school. J-QUEST comprises a quantitative, 70 kHz, split-beam echosounder and a stereo-video camera. It was deployed from a research vessel to collect concomitant measures of TS and stereo images of in situ Pacific saury and Japanese anchovy. The stereo-video camera provides estimates of the fish lengths (L) and tilt-angles corrected for J-QUEST motion. In this way, empirical models of TS vs. log(L) were derived for Pacif...

Basin-scale distribution pattern and biomass estimation of Japanese anchovy Engraulis japonicus in the western North Pacific

Fisheries Science, 2012

The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore ... more The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore region of the western North Pacific (north of 35°N and west of 170°E) were studied using a quantitative echosounder. This is the first attempt at such a study in this region. Data were collected in summer from 2004 to 2007. The biomass was estimated using data collected at 38 kHz. Species compositions in the backscatterings from pelagic fish were assigned based on the results of trawl hauls taking account of sea surface temperature (SST). Japanese anchovy tended to be high density to the west of 153°E and were distributed in an SST range of 9-24 °C. Although the temporal and spatial coverage of the survey differed each year, at least 1.5-3.4 million tons of Japanese anchovy were present in the survey area between 2004 and 2007. To take account of the spatial coverage of the survey each year, the most reliable biomass estimate for this region in the time period was 3.4 million tons (coefficient of variation 0.22).

魚類の腹腔内に挿入したピンガの送波音圧の変化

NIPPON SUISAN GAKKAISHI, 2011

Swimbladder Shape and Relationship Between Target Strength and Body Length of Japanese Anchovy (Engraulis japonicus)

The Journal of the Marine Acoustics Society of Japan, 2010

Effect of Depth-Dependent Target Strength on Biomass Estimation of Japanese Anchovy

Journal of Marine Science and Technology, 2011

We express thanks to all of the researchers and crews who were engaged in the survey. Comments fr... more We express thanks to all of the researchers and crews who were engaged in the survey. Comments from two anonymous reviewers and the guest editor, Dr. Masahiko Furusawa, greatly improved the contents of the manuscript. This survey was supported by the Fisheries Agency of Japan, the Fisheries Research Agency of Japan and the Institute of Cetacean Research. We thank these institutions for their support. The results of this paper was initially presented to the Asian Fisheries Acoustics Society (AFAS) 2009 meeting "The International Conference on Fisheries Acoustics and Contribution for Sustainable Fisheries in Asia". We express thanks to the conveners of the meeting who provided us such opportunity.

Precise target strength measurement and morphological observation of juvenile walleye pollock (Theragra chalcogramma)

Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600)

This study examines a relationship between target strength (TS) and fork length (FL) for walleye ... more This study examines a relationship between target strength (TS) and fork length (FL) for walleye pollock at the juvenile stage. Dozens of juvenile walleye pollock were caught by a set net nearby spawning area in Pacific coast of southern Hokkaido. These juveniles were kept for a year in a tank and measured periodically with growth. Samples were anesthetized and treated

Acoustic characteristics of vertically migrating and non-migrating organisms observed in the North Pacific Ocean

The Journal of the Acoustical Society of America, 2008

Acoustic characteristics of vertically migrating and non-migrating organisms in a day were invest... more Acoustic characteristics of vertically migrating and non-migrating organisms in a day were investigated for species identification. In July 27-30, 2004, both organisms were observed using ship echosounders (38 kHz and 120 kHz) and a tethered acoustic-optical composite system (J-QUEST) from several hours before sunset to several hours after the sunrise, drifting a research vessel, Shunyo-maru, in the North Pacific Ocean. The J-QUEST is an instrumental package composed of an split-beam echosounder (70 kHz) and a stereo TV camera system. The J-QUEST depth was changed from 220 m to 25 m to observe vertical migration. Boreopacific gonate squids were observed by the stereo TV camera and they are considered to conduct diurnal vertical migration to feed migrating organisms. Average TS of the ascending layer and Boreopacific squid were measured in situ using the J-QUEST. Average area scattering strength (SA) values of the ascending layer, non-migrating layer, descending layer, aggregation of...

Target strength of a mesopelagic fish Maurolicus japonicus at 38 and 120 kHz

The Journal of the Acoustical Society of America, 2006

Target strength (TS) of Maurolicus japonicus was examined at 38 and 120 kHz using experimental me... more Target strength (TS) of Maurolicus japonicus was examined at 38 and 120 kHz using experimental measurements (at 38 kHz) and theoretical swimbladder scattering models. Experimental measurements showed that the average TS for dominant size (32.1 to 34.8 mm standard length) were −60.5 to −56.7 dB, and the effect of the fish orientation on TS was slight. These results coincided with the model estimation, proving that swimbladder models are valid to estimate the TS of M. japonicus. The slight effect of the fish orientation on TS was presumed due to the oval shaped swimbladder with high aspect ratio, which is relatively little to the wavelength. This is a merit because tilt angle is usually a major source of TS variation. However, a little swimbladder would cause acoustic resonance at low frequencies, which leads to insatiability on TS according to depth change. Using the resonant model, relationships of the TS and standard length were estimated for depth 50, 100, 150, 200, and 250 m at 3...

Swimbladder morphology and target strength of myctophid fish of the northwestern Pacific

The Journal of the Acoustical Society of America, 2006

Swimbladder shapes of fish from 14 myctophid species captured around Japan were measured using an... more Swimbladder shapes of fish from 14 myctophid species captured around Japan were measured using an x-ray method to estimate the theoretical target strength. Using those x-ray images, the fish were classified into bladder species and nonbladder species according to the presence of the gas. Five species had no swimbladder in any body size range examined. Others contained bladder and nonbladder fishes in relation to growth. The growth of swimbladder length was not proportional to that of body length (allometric growth) in some bladder fishes. Based on morphological parameters of the body and swimbladder, the relationships between body length and target strength from 38 to 200 kHz were estimated using theoretical acoustical backscattering models. Estimated values of target strength showed greater than 10-dB differences between bladder and nonbladder fishes, even when the fish were of equivalent size. Because of the allometric growth of the swimbladder, values of the target strength were ...

Influence of Body Bend by Swimming Activity on Fish Target Strength

The Journal of the Marine Acoustics Society of Japan, 2005

Estimation of target strength of Sardina pilchardus and Sardinella aurita by theoretical approach

Fisheries Science, 2016

The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz w... more The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz were estimated by a prolate-spheroid 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 6-9 dB higher for S. pilchardus and 5-7 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.

Tilt Angle and Theoretical Target Strength of the Japanese Sandeel, Ammodytes personatus, Captured on the Northern Coast of Hokkaido

The Journal of the Marine Acoustics Society of Japan, 2013

The tilt angle, i.e., the angle from horizontal made by the fish body as its head dives down or u... more The tilt angle, i.e., the angle from horizontal made by the fish body as its head dives down or up, affects the readings on fish echo soundings. We measured the tilt angle of Japanese sandeels (Ammodytes personatus Girard) in a water tank, and calculated the acoustic target strength (TS) using a theoretical scattering model. This study examined the TS of sandeels from the northern coast of Hokkaido, which have a larger body size than those in other regions in Japan. TS values for sandeels, a swimbladderless fish, were estimated using a distorted-wave Born approximation (DWBA) model at two frequencies: 38 and 120 kHz. The mean tilt angle was 20.4° (S.D.=18.5°), which differed slightly from that of the lesser sandeel, Ammodytes marinus. The regression equations of the average TS values were TS 38 kHz =8.2 log 10 SL-74.2 and TS 120 kHz =20.9 log 10 SL-92.6, respectively. At 120 kHz, the slope was close to 20, suggesting that the acoustic backscattering strength was proportional to the square of the body length. This value was smaller at 38 kHz, suggesting that the acoustic backscattering strength was stable to differences in body length. We obtained a small discrepancy for both frequencies (ΔTS=TS 120 kHz -TS 38 kHz ) were TS 120 kHz <TS 38 kHz . Discrepancies of -1.3 dB for the maximum TS, and -1.8 dB for averaged TS were found in 72 fish samples, which would be useful for identifying sandeel schools in practical analysis using TS differences.

Measurements of Sound-Speed in the Tissue of Juvenile Southern Bluefin Tuna (Thunnus maccoyii) for Target Strength Estimation

The Journal of the Marine Acoustics Society of Japan, 2007

＊ 2 Kozo TOKUYAMA (FURUNO Electoric Co.) ターゲットストレングス推定に必要なミナミマグロ (Thunnus maccoyii) 幼魚の魚肉内音速測定 ... more

A Connection Model between the Positioning Mechanism and Ultrasonic Measurement System via a Web Browser to Assess Acoustic Target Strength

SICE Journal of Control, Measurement, and System Integration, 2009

This paper details a network-controlled measurement system for use in fisheries engineering. The ... more This paper details a network-controlled measurement system for use in fisheries engineering. The target strength (TS) of fish is important in order to convert acoustic integration values obtained during acoustic surveys into estimates of fish abundance. The target strength pattern is measured with the combination of the rotation system for the aspect of the sample and the echo data acquisition system using the underwater supersonic wave. The user interface of the network architecture is designed for collaborative use with researchers in other organizations. The flexible network architecture is based on the web direct-access model for the rotation mechanism. The user interface is available for monitoring and controlling via a web browser that is installed in any terminal PC (personal computer). Previously the combination of two applications was performed not by a web browser but by the exclusive interface program. So a connection model is proposed between two applications by indirect communication via the DCOM (Distributed Component Object Model) server and added in the web direct-access model. A prompt report system in the TS measurement system and a positioning and measurement system using an electric flatcar via a web browser are developed. By a secure network architecture, DCOM communications via both Intranet and LAN are successfully certificated.

Application of broadband dolphin mimetic sonar for discriminating target fish species

For the acoustic species discrimination, broadband response of three tuna species, bigeye tuna, y... more For the acoustic species discrimination, broadband response of three tuna species, bigeye tuna, yellowfin tuna and skipjack tuna were measured by a broadband split beam sonar system. Each species was kept in an enclosure separately. Ultrasonic broadband sound (70 kHz -140kHz) was projected nearly horizontally to the captive fish body in a floating pen. Three major echoes were detected from each fish. The delay time between earlier and last echo corresponded to the body width of the target fish. These echoes seemed to come from the left and right body surface of each fish when the acoustic beam projected transversally to the fish body. The dominant echo at the middle between body surface echoes was considered to come from the center of the body such as the swimbladder and/or the spine. As already known, bigeye tuna has swimbladder where as skipjack tuna does not. Yellowfin tuna has smaller swimblader than that of bigeye tuna. The relative intensity of the body surface echo to the body center echo was large for skipjack tuna and small for bigeye tuna. This is consistent with the large target strength of the swimbladder rather than the spine or other unidentified reflectors in the body center of the fish. This could be a key for the species discrimination. More sample size and experiment including numerical simulation is needed as the future research.

Development of an acoustic-optical system to estimate target-strengths and tilt angles from fish aggregations

Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600)

The J-QUEST instrument package, a quantitative 70kHz split-beam echo sounder and a stereo TV came... more The J-QUEST instrument package, a quantitative 70kHz split-beam echo sounder and a stereo TV camera, is being developed to observe mesopelagic fish. In situ acoustic and optical measurements of single fish within aggregations include swimming speed, target strength, length, and tilt angle. Acoustic data and two video signals are monitored in real-time via an optical-power composite cable and receivers on deck. The J-QUEST was deployed from the R/V Kaiyo-maru in the transient waters of the Kuroshio current from Kashima-nada to off the coast of Sanriku in the east of Japan. J-QUEST was tethered from the surface to a depth of 200m and worked well. In Kashima-nada at a depth of 10m, Pacific saury (Cololabis saira) were attracted to the underwater lights and formed a large aggregation around J-QUEST. We could monitor fish on both the TV monitors and on the echogram. Average target strength of Pacific saury was -37.9dB and normalized TS (by squared fork length) was -66.8dB.

Swimbladders under pressure: anatomical and acoustic responses by walleye pollock

ICES Journal of Marine Science, 2009

Horne, J. K., Sawada, K., Abe, K., Kreisberg, R. B., Barbee, D. H., and Sadayasu, K. 2009. Swimbl... more Horne, J. K., Sawada, K., Abe, K., Kreisberg, R. B., Barbee, D. H., and Sadayasu, K. 2009. Swimbladders under pressure: anatomical and acoustic responses by walleye pollock. – ICES Journal of Marine Science, 66: 1162–1168. Pressure influences echo intensities from fish through changes in swimbladder volumes and surface areas. Volume reduction is expected to correspond to Boyle’s law (volume α pressure−1), but the effects of deforming the dorsal-aspect surface area of the swimbladder on the target strength (TS) of a physoclist have not been quantified at geometric scattering frequencies. Dorsal and lateral radiographs of three juvenile walleye pollock (Theragra chalcogramma) in a pressure chamber were used to image swimbladders from ambient to a maximum of 4.9 × 105 Pa (i.e. 5 atm). Radiographs from an additional 16 0-group, 21 juvenile, and 28 adult fish were used to compare swimbladder sizes and shapes across life-history stages. The directional elliptical eccentricity, which descr...

Target-strength, length, and tilt-angle measurements of Pacific saury (Cololabis saira) and Japanese anchovy (Engraulis japonicus) using an acoustic-optical system

ICES Journal of Marine Science, 2009

Sawada, K., Takahashi, H., Abe, K., Ichii, T., Watanabe, K., and Takao, Y. 2009. Target-strength,... more Sawada, K., Takahashi, H., Abe, K., Ichii, T., Watanabe, K., and Takao, Y. 2009. Target-strength, length, and tilt-angle measurements of Pacific saury (Cololabis saira) and Japanese anchovy (Engraulis japonicus) using an acoustic-optical system. – ICES Journal of Marine Science, 66: 1212–1218. Pacific saury and Japanese anchovy generally congregate in dense groups or schools. An acoustic-optical system (the Japanese Quantitative Echosounder and Stereo-video Camera System or J-QUEST) has been developed to measure accurately the target strength (TS) of fish in a dense school. J-QUEST comprises a quantitative, 70 kHz, split-beam echosounder and a stereo-video camera. It was deployed from a research vessel to collect concomitant measures of TS and stereo images of in situ Pacific saury and Japanese anchovy. The stereo-video camera provides estimates of the fish lengths (L) and tilt-angles corrected for J-QUEST motion. In this way, empirical models of TS vs. log(L) were derived for Pacif...

Basin-scale distribution pattern and biomass estimation of Japanese anchovy Engraulis japonicus in the western North Pacific

Fisheries Science, 2012

The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore ... more The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore region of the western North Pacific (north of 35°N and west of 170°E) were studied using a quantitative echosounder. This is the first attempt at such a study in this region. Data were collected in summer from 2004 to 2007. The biomass was estimated using data collected at 38 kHz. Species compositions in the backscatterings from pelagic fish were assigned based on the results of trawl hauls taking account of sea surface temperature (SST). Japanese anchovy tended to be high density to the west of 153°E and were distributed in an SST range of 9-24 °C. Although the temporal and spatial coverage of the survey differed each year, at least 1.5-3.4 million tons of Japanese anchovy were present in the survey area between 2004 and 2007. To take account of the spatial coverage of the survey each year, the most reliable biomass estimate for this region in the time period was 3.4 million tons (coefficient of variation 0.22).

魚類の腹腔内に挿入したピンガの送波音圧の変化

NIPPON SUISAN GAKKAISHI, 2011

Swimbladder Shape and Relationship Between Target Strength and Body Length of Japanese Anchovy (Engraulis japonicus)

The Journal of the Marine Acoustics Society of Japan, 2010

Effect of Depth-Dependent Target Strength on Biomass Estimation of Japanese Anchovy

Journal of Marine Science and Technology, 2011

We express thanks to all of the researchers and crews who were engaged in the survey. Comments fr... more We express thanks to all of the researchers and crews who were engaged in the survey. Comments from two anonymous reviewers and the guest editor, Dr. Masahiko Furusawa, greatly improved the contents of the manuscript. This survey was supported by the Fisheries Agency of Japan, the Fisheries Research Agency of Japan and the Institute of Cetacean Research. We thank these institutions for their support. The results of this paper was initially presented to the Asian Fisheries Acoustics Society (AFAS) 2009 meeting "The International Conference on Fisheries Acoustics and Contribution for Sustainable Fisheries in Asia". We express thanks to the conveners of the meeting who provided us such opportunity.

Precise target strength measurement and morphological observation of juvenile walleye pollock (Theragra chalcogramma)

Oceans '04 MTS/IEEE Techno-Ocean '04 (IEEE Cat. No.04CH37600)

This study examines a relationship between target strength (TS) and fork length (FL) for walleye ... more This study examines a relationship between target strength (TS) and fork length (FL) for walleye pollock at the juvenile stage. Dozens of juvenile walleye pollock were caught by a set net nearby spawning area in Pacific coast of southern Hokkaido. These juveniles were kept for a year in a tank and measured periodically with growth. Samples were anesthetized and treated

Acoustic characteristics of vertically migrating and non-migrating organisms observed in the North Pacific Ocean

The Journal of the Acoustical Society of America, 2008

Acoustic characteristics of vertically migrating and non-migrating organisms in a day were invest... more Acoustic characteristics of vertically migrating and non-migrating organisms in a day were investigated for species identification. In July 27-30, 2004, both organisms were observed using ship echosounders (38 kHz and 120 kHz) and a tethered acoustic-optical composite system (J-QUEST) from several hours before sunset to several hours after the sunrise, drifting a research vessel, Shunyo-maru, in the North Pacific Ocean. The J-QUEST is an instrumental package composed of an split-beam echosounder (70 kHz) and a stereo TV camera system. The J-QUEST depth was changed from 220 m to 25 m to observe vertical migration. Boreopacific gonate squids were observed by the stereo TV camera and they are considered to conduct diurnal vertical migration to feed migrating organisms. Average TS of the ascending layer and Boreopacific squid were measured in situ using the J-QUEST. Average area scattering strength (SA) values of the ascending layer, non-migrating layer, descending layer, aggregation of...

Target strength of a mesopelagic fish Maurolicus japonicus at 38 and 120 kHz

The Journal of the Acoustical Society of America, 2006

Target strength (TS) of Maurolicus japonicus was examined at 38 and 120 kHz using experimental me... more Target strength (TS) of Maurolicus japonicus was examined at 38 and 120 kHz using experimental measurements (at 38 kHz) and theoretical swimbladder scattering models. Experimental measurements showed that the average TS for dominant size (32.1 to 34.8 mm standard length) were −60.5 to −56.7 dB, and the effect of the fish orientation on TS was slight. These results coincided with the model estimation, proving that swimbladder models are valid to estimate the TS of M. japonicus. The slight effect of the fish orientation on TS was presumed due to the oval shaped swimbladder with high aspect ratio, which is relatively little to the wavelength. This is a merit because tilt angle is usually a major source of TS variation. However, a little swimbladder would cause acoustic resonance at low frequencies, which leads to insatiability on TS according to depth change. Using the resonant model, relationships of the TS and standard length were estimated for depth 50, 100, 150, 200, and 250 m at 3...

Swimbladder morphology and target strength of myctophid fish of the northwestern Pacific

The Journal of the Acoustical Society of America, 2006

Swimbladder shapes of fish from 14 myctophid species captured around Japan were measured using an... more Swimbladder shapes of fish from 14 myctophid species captured around Japan were measured using an x-ray method to estimate the theoretical target strength. Using those x-ray images, the fish were classified into bladder species and nonbladder species according to the presence of the gas. Five species had no swimbladder in any body size range examined. Others contained bladder and nonbladder fishes in relation to growth. The growth of swimbladder length was not proportional to that of body length (allometric growth) in some bladder fishes. Based on morphological parameters of the body and swimbladder, the relationships between body length and target strength from 38 to 200 kHz were estimated using theoretical acoustical backscattering models. Estimated values of target strength showed greater than 10-dB differences between bladder and nonbladder fishes, even when the fish were of equivalent size. Because of the allometric growth of the swimbladder, values of the target strength were ...

Influence of Body Bend by Swimming Activity on Fish Target Strength

The Journal of the Marine Acoustics Society of Japan, 2005