Acoustic identification of isada krill, <i>Euphausia pacifica</i> Hansen, off the Sanriku coast, north‐eastern Japan

Miyashita, Kazushi; Aoki, Ichiro; Seno, Koutaro; Taki, Kenji; Ogishima, Takashi

doi:10.1046/j.1365-2419.1998.00042.x

Cited by 49 publications

(24 citation statements)

References 13 publications

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“…The primary species of myctophids in our study area (Sinclair and Stabeno 2002) have swimbladders, although some species (including Stenobrachius leucopsarus, the numerically dominant species) undergo an ontogenetic shift from a primarily gas-filled swimbladder to a lipid-filled swimbladder (Butler and Pearcy 1972). These results indicate that it should be possible to distinguish backscatter from swimbladdered fishes and euphausiids based on the large difference in observed relative frequency response as has been previously reported (e.g., Miyashita et al 1997;McKelvey and Wilson 2006), and likely jellyfish and myctophids as well.…”

Section: Empirical Measurement Of Relative Frequency Responsesupporting

confidence: 76%

Development and application of an empirical multifrequency method for backscatter classification

Robertis

McKelvey

Ressler

2010

Can. J. Fish. Aquat. Sci.

132

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We evaluated the feasibility of identifying major acoustic scatters in North Pacific ecosystems based on empirical measurements of relative frequency response. Acoustic measurements in areas where trawl catches were dominated by single taxa indicated that it might be possible to discern among key groups of scatterers such as fish with gas-filled swimbladders, euphausiids, myctophids, and jellyfish. To establish if walleye pollock (Theragra chalcogramma), a key species in the ecosystem, can be separated reliably from other groups under prevailing conditions, we developed a method based on the normal deviate (or Z score) to identify backscatter consistent with the pollock relative frequency response. We evaluated the performance of the method by comparing it with the traditional method of species identification (i.e., directed trawl catches and subjective interpretation of echograms) during five large-scale acoustic surveys of the eastern Bering Sea. Pollock abundance estimates employing the multifrequency method were highly correlated with those using the traditional method, which indicates that the multifrequency method performs well in this situation. In this environment, multifrequency methods will allow more inferences to be drawn when direct sampling of organisms is limited and will also complement existing abundance surveys by improving species classification and providing information about key nontarget species.Résumé : Nous évaluons la faisabilité d'identifier les principales rétrodiffusions acoustiques dans les écosystèmes du Pacifique Nord, d'après des mesures empiriques des fréquences relatives des réponses. Les mesures acoustiques dans les ré-gions dans lesquelles les prises au chalut sont dominées par un seul taxon indiquent qu'il devrait être possible de discerner les groupes principaux d'organismes responsables de la rétrodiffusion, tels que les poissons avec vessie natatoire remplie de gaz, les euphausiidés, les myctophidés et les méduses. Afin d'établir si la goberge de l'Alaska (Theragra chalcogramma), une espèce dominante de l'écosystème, peut être distinguée de façon fiable des autres groupes dans les conditions actuelles, nous avons mis au point une méthode basée sur l'écart normal (ou cote Z) pour identifier la rétrodiffusion correspondant aux fréquences relatives des réponses de la goberge. Nous avons évalué la performance de la méthode en la comparant avec la méthode traditionnelle d'identification des espèces (c'est-à-dire des récoltes dirigées au chalut et une interprétation subjective des échogrammes) durant cinq inventaires acoustiques à grande échelle dans l'est de la mer de Bé-ring. Il existe une forte corrélation entre les estimations de l'abondance des goberges de l'Alaska basées sur la méthode des fréquences multiples et celles tirées de la méthode traditionnelle, ce qui indique que la méthode des fréquences multiples fonctionne bien dans les circonstances. Dans cet environnement, les méthodes des fréquences multiples permettront de faire plus de déductions lorsque l'échantillonnag...

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Section: Empirical Measurement Of Relative Frequency Responsesupporting

confidence: 76%

Development and application of an empirical multifrequency method for backscatter classification

Robertis

McKelvey

Ressler

2010

Can. J. Fish. Aquat. Sci.

132

View full text Add to dashboard Cite

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“…Miyashita et al . reported the TS difference (ΔTS 120 kHz−38 kHz ), used to separate krill aggregations from scatter, fell within a range from 10 to 15 dB using a theoretical model and the swimming behavior of E. pacifica 6 . Krill body length was found to range between 11 and 28 mm.…”

Section: Discussionmentioning

confidence: 90%

“…However, most of these studies have been restricted to the investigation of migration and distribution patterns, and have not involved species identification, because it is impossible to discriminate specific targets from combined echo signals using the ADCP alone. Recently, however, the mean volume backscattering strength difference (ΔMVBS) method, using multifrequency data, has been used for species identification of fish and zooplankton 6,7 …”

Section: Introductionmentioning

confidence: 99%

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

et al. 2004

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An application of the acoustic Doppler current profiler (ADCP, 153.6 kHz) in combination with a scientific echo sounder (EK60, 38 and 200 kHz) was investigated to estimate the density of krill Euphausia pacifica. The acoustic backscattering strength from sound scattering layers was compared with biomass estimates from midwater trawls. Euphausia pacifica was targeted among mixed species populations in the sound scattering layer in the offshore Funka Bay area of Hokkaido, Japan. The frequency characteristics of acoustic backscattering by krill were calculated using a distorted wave Born approximation scattering model at three frequencies. Krill aggregations identified from the EK60 data were extracted as the mean volume backscattering strength difference between two frequencies. They were then used to identify similar aggregations in the ADCP data by matching observation times and depths for the two methods, which were applied simultaneously. Results from the comparison of the mean volume backscattering strength and the density calculated from the ADCP and EK60 showed that ADCP can be used to measure density and spatial-temporal distribution of krill aggregations. Current speed and direction at the study site were found to be 16.1 cm/s and 187.0∞, respectively, and krill speed and direction (including the current component) were found to be 19.8 cm/s and 172.2∞, respectively. Based on the ADCP data, the net speed and direction of the krill aggregations were found to be 5.9 cm/s and 128.0∞, respectively.KEY WORDS: acoustic Doppler current profiler, distorted wave Born approximation model, echo intensity, Euphausia pacifica identification, krill identification, mean volume backscattering strength, scientific echosounder.

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“…Analyses of the distribution and abundance of euphausiids were based on samples collected every two months using 5.5‐m‐long cylindrical‐conical nets (diameter 1.3 m, mesh size 0.45 mm) 28 in coastal waters off south‐eastern Hokkaido (41°–43°N), Sanriku (38°–41°N), and Joban (36°–38°N) from March 1997 to February 1998 25 . Either two or three transects were set for each coastal water, and a zigzag line between 100 and 300‐m isobaths off Sanriku and Joban was added in March and April, to conduct an acoustic survey 29 . Off Sanriku and Joban, the survey stations were set at approximately 100, 200, 300, 500, and 1000‐m isobaths.…”

Section: Methodsmentioning

confidence: 99%

Seasonal changes in distribution and abundance of euphausiids in the coastal area of north-eastern Japan

Taki

2007

Fisheries Sci

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Seasonal changes in distribution and abundance of euphausiids off south-eastern Hokkaido (41°-43°N), Sanriku (38°-41°N), and Joban (36°-38°N) were investigated using cylindricalconical nets every two months from March 1997 to February 1998. Twenty-six species of seven genera of euphausiids occurred during the survey. Among them, subarctic-transitional Euphausia pacifica was the most abundant throughout the year in coastal waters, as their relative contribution to the total abundance of euphausiids was 89-92%. This species occurred in each coastal water throughout the survey and was abundant from winter to early summer (February-June) off Sanriku and Joban and in autumn in south-eastern Hokkaido. Thysanoessa inspinata occurred off southeastern Hokkaido and Sanriku throughout the survey, mainly in spring (April) but rarely occurred off Joban. Three other subarctic Thysanoessa species occurred mainly off south-eastern Hokkaido from winter to spring. Conversely, warm-and transitional-water epipelagic species occurred exclusively off Sanriku and Joban in autumn. The characteristics of seasonal distributional patterns of euphausiids are discussed in relation to the spatial and temporal changes of oceanographic conditions and several predators off north-eastern Japan.

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Acoustic identification of isada krill, Euphausia pacifica Hansen, off the Sanriku coast, north‐eastern Japan

Cited by 49 publications

References 13 publications

Development and application of an empirical multifrequency method for backscatter classification

Development and application of an empirical multifrequency method for backscatter classification

Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

Seasonal changes in distribution and abundance of euphausiids in the coastal area of north-eastern Japan

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