scholarly journals IN SITU AND EX SITU TARGET STRENGTH MEASUREMENT OF MESOPELAGIC LANTERNFISH, DIAPHUS THETA (FAMILY MYCTOPHIDAE)

2011 ◽  
Vol 19 (3) ◽  
Author(s):  
Kouichi Sawada ◽  
Kazuhisa Uchikawa ◽  
Tomohiko Matsuura ◽  
Hiroya Sugisaki ◽  
Kazuo Amakasu ◽  
...  
Keyword(s):  
Ex Situ ◽  
Target Strength ◽  
Strength Measurement ◽  
Diaphus Theta

scholarly journals In situ target-strength measurement of young hairtail (Trichiurus haumela) in the Yellow Sea

2006 ◽  
Vol 63 (1) ◽  
pp. 46-51 ◽  
Author(s):  
Xianyong Zhao
Keyword(s):  
Confidence Interval ◽  
Yellow Sea ◽  
The Yellow Sea ◽  
Target Strength ◽  
Abundance Estimation ◽  
Strength Measurement ◽  
The Mean

Abstract The target strength of hairtail (Trichiurus haumela) in the Yellow Sea was measured in situ with a 38 kHz, split-beam echosounder on 2 January 2001. The fish measured were of the 2000 year class, its anal length ranged from 62 to 115 mm, with a mean of 89.8 mm. The mean target strength of these young hairtail was estimated to be −49.2 dB, with a 95% confidence interval of (−49.4, −49.0) dB. This provided a rare and useful reference for the acoustic-abundance estimation of hairtail.

scholarly journals Multifrequency target strength of northern krill (Meganyctiphanes norvegica) swimming horizontally

2011 ◽  
Vol 69 (1) ◽  
pp. 119-130 ◽  
Author(s):  
Lucio Calise ◽  
Tor Knutsen
Keyword(s):  
Length Distribution ◽  
Ex Situ ◽  
Target Strength ◽  
Acoustic Backscatter ◽  
Acoustic Measurements ◽  
Acoustic Beams ◽  
Meganyctiphanes Norvegica ◽  
Acoustic Identification ◽  
Made In

Abstract Calise, L., and Knutsen, T. 2012. Multifrequency target strength of northern krill (Meganyctiphanes norvegica) swimming horizontally. – ICES Journal of Marine Science, 69: 119–130. Multifrequency acoustic measurements on ex situ horizontally swimming krill were made in a novel experimental setting. An ensemble of northern krill (Meganyctiphanes norvegica) was introduced to a large enclosure (a mesocosm), and acoustic backscatter was sampled using a multifrequency (70, 120, and 200 kHz) echosounder (Simrad EK60). Two submerged lamps were placed at opposite sides of the mesocosm and switched on and off to induce the krill, by light attraction, to swim horizontally through the acoustic beams. By tracking echoes, animal displacement, swimming speed, and target strength (TS) by frequency were estimated. The dominant and secondary modes of the total-length distribution were 21.8 ± 3.0 and 27.8 ± 2.7 mm, respectively. Although krill orientation was assumed stable and the ping rate was high, the range and inter-ping variability of the average TS values were large, decreasing and increasing with frequency, respectively. The overall TS frequency response observed and concurrent measurements at 120 and 200 kHz confirm the theoretical expectation that the acoustic backscatter from the investigated organisms were confined to the Rayleigh and Geometric scattering regions, a finding that might both aid acoustic identification and size-group separation of in situ northern krill.

Ex situ and in situ measurements of juvenile yellowfin tuna Thunnus albacares target strength

2011 ◽  
Vol 77 (6) ◽  
pp. 903-913 ◽  
Author(s):  
Hsueh-Jung Lu ◽  
Myounghee Kang ◽  
Hsing-Han Huang ◽  
Chi-Chang Lai ◽  
Long-Jin Wu
Keyword(s):  
Yellowfin Tuna ◽  
In Situ Measurements ◽  
Ex Situ ◽  
Target Strength ◽  
Thunnus Albacares

scholarly journals Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel

2009 ◽  
Vol 66 (6) ◽  
pp. 1169-1175 ◽  
Author(s):  
Tonje Lexau Nesse ◽  
Halvor Hobæk ◽  
Rolf J. Korneliussen
Keyword(s):  
Frequency Response ◽  
Acoustic Scattering ◽  
Ex Situ ◽  
Target Strength ◽  
Model Parameters ◽  
Acoustic Frequency ◽  
Atlantic Mackerel ◽  
Scattering Spectra ◽  
Laboratory Tank

Abstract Nesse, T. L., Hobæk, H., and Korneliussen, R. J. 2009. Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel. – ICES Journal of Marine Science, 66: 1169–1175. Atlantic mackerel (Scomber scombrus) are weak sound scatterers compared with fish that have swimbladders. Accurate acoustic estimates of mackerel abundance require estimates of target strength. Different parts of mackerel may dominate the backscattering spectra. Mackerel schools are acoustically recognized mainly by backscatter four times stronger at 200 kHz than at 38 kHz. Simulations have established that backscatter from only the flesh and the backbone could explain this frequency response, although there are uncertainties in the model parameters and simplifications. In this paper, experiments conducted in a laboratory tank to investigate the complexity of mackerel backscatter are discussed. Acoustic backscatter was measured over the frequency range 65–470 kHz from individual dead mackerel, and their backbones, heads, and skulls. Backscatter from the backbones was measured at several angles of incidence. Grating lobes (Bragg scattering) appeared at different angles, depending on the acoustic frequency and the spacing of the vertebrae. These lobes were evident in backbone backscatter after propagating through the flesh and can be used, in principle, to determine mackerel size acoustically. The frequency response of individual, ex situ Atlantic mackerel estimated from these measurements did not match that from the measurements of in situ mackerel schools. Further investigation is warranted.

Comparison of in situ, ex situ, and backscatter model estimates of Pacific hake (Merluccius productus) target strength

2007 ◽  
Vol 64 (12) ◽  
pp. 1781-1794 ◽  
Author(s):  
Mark J Henderson ◽  
John K Horne
Keyword(s):  
Acoustic Energy ◽  
Common Method ◽  
Ex Situ ◽  
Target Strength ◽  
Fish Density ◽  
Fish Length ◽  
Merluccius Productus

To convert acoustic energy into estimates of fish density, the target strength (TS) of a representative fish must be known. TS is a measure of the acoustic reflectivity of a fish, which is variable depending on the presence of a swimbladder, the size of the fish, its behavior, morphology, and physiology. The most common method used to estimate the TS of a fish is a TS-to-length empirical regression, with TS values increasing with fish length. This study uses in situ and ex situ TS measurements and a backscatter model to develop TS-to-length conversions for Pacific hake (Merluccius productus). Results from in situ and ex situ measurements had regression intercepts 4–6 dB lower than the previous Pacific hake TS-to-length regression. These differences suggest that an individual hake reflects 2.5–4 times less acoustic energy than was previously estimated.

scholarly journals Estimating the target strength of live, free-swimming chokka squid Loligo reynaudii at 38 and 120 kHz

2010 ◽  
Vol 67 (7) ◽  
pp. 1381-1391 ◽  
Author(s):  
Michael A. Soule ◽  
Ian Hampton ◽  
Marek R. Lipiński
Keyword(s):  
Ex Situ ◽  
Target Strength ◽  
Research Vessel ◽  
Free Swimming ◽  
Spawning Aggregations ◽  
Backscattering Cross Section ◽  
In Situ Experiments ◽  
In The Wild ◽  
Loliginid Squid

Abstract Soule, M. A., Hampton, I., and Lipiński, M. R. 2010. Estimating the target strength of live, free-swimming chokka squid Loligo reynaudii at 38 and 120 kHz. – ICES Journal of Marine Science, 67: 1381–1391. Estimates of the target strength (TS) of the loliginid squid Loligo reynaudii at 120 kHz were made from ex situ experiments on 38 caged, but free-swimming animals, and at 38 and 120 kHz from 17 in situ experiments on spawning aggregations in the wild conducted from a research vessel and from small boats. The cage experiments suggested that the backscattering cross section is proportional to mantle length (ML), which would not be expected from simple considerations of ML in relation to wavelength. A similar relationship was found during the in situ experiments conducted from the research vessel. The TS estimates from the research vessel agreed well with those from the cage experiments, for both of the two methods used to extract squid TS distributions from the overall TS distributions, but were some 2–3 dB lower than those from the small boats. This suggests that in situ estimates are affected by the vessel and/or the way in which squid react to it. It is concluded that ex situ experiments on L. reynaudii TS are of most value as a complement to in situ experiments, which should be made concurrently while surveying, using systems capable of having higher volume resolution than in the current experiments, to maximize the applicability of the estimates to the survey data.

scholarly journals Variations in the target strength of Atlantic cod during vertical migration

2009 ◽  
Vol 66 (6) ◽  
pp. 1205-1211 ◽  
Author(s):  
George A. Rose
Keyword(s):  
Vertical Migration ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Multivariate Model ◽  
Ex Situ ◽  
Target Strength ◽  
Conventional Model ◽  
Close Range ◽  
The Mean

Abstract Rose, G. A. 2009. Variations in the target strength of Atlantic cod during vertical migration. – ICES Journal of Marine Science, 66: 1205–1211. Experiments conducted at sea in June 1999 and January 2000 indicated that the mean target strength (TS) of Atlantic cod (Gadus morhua) varies not just with length, but also with pressure (depth) and fish orientation, particularly during vertical migration. In June, when fish were migrating and spawning, vertical migration was pronounced, extending up to 150 m off the seabed, and the associated TS declined by as much as 5 dB. In January, when the fish were located nearer the seabed, mean TS was more stable and matched a conventional model of TS vs. length [L, cm; i.e. TS = 20 log(L) − 66] based on measurements of ex situ fish orientated horizontally and positioned at close range. This paper demonstrates that mean TS is inversely related (p < 0.05) to the range off the seabed (r, m), which includes 90% of fish. Based on this finding, a new multivariate TS model is proposed: TS = 20 log(L) − 65 − 0.05 r. In this model, r is a proxy for swimbladder volume and fish orientation. A survey in May 2007 found that cod (mean L = 63 cm) dispersed in such a way that single targets could be resolved up to 100 m from the seabed. Measurements of TS of in situ individual fish (TSindividual) and mean TS inferred from a comparison of area-backscattering coefficients (sa) and count-based densities (TSindirect) were positively correlated with a slope not different from unity. Means of these TS estimates were −32.4 and −32.2 dB, respectively, or ∼2.3 dB less than that predicted by the conventional model. In contrast, the new multivariate model predicts TS = −32.5 dB, which is nearly identical with the means of TSindividual and TSindirect.

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