scholarly journals Comparison of walleye pollock target strength estimates determined from in situ measurements and calculations based on swimbladder form

1988 ◽  
Vol 83 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Kenneth G. Foote ◽  
Jimmie J. Traynor
Keyword(s):  
Walleye Pollock ◽  
In Situ Measurements ◽  
Target Strength

scholarly journals In situ measurements of capelin (Mallotus villosus) target strength in the North Pacific Ocean

2008 ◽  
Vol 66 (2) ◽  
pp. 258-263 ◽  
Author(s):  
Michael A. Guttormsen ◽  
Christopher D. Wilson
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
In Situ Measurements ◽  
Target Strength ◽  
Mallotus Villosus ◽  
The North ◽  
Capelin Mallotus Villosus ◽  
The North Pacific

Abstract Guttormsen, M. A. and Wilson, C. D. 2009. In situ measurements of capelin (Mallotus villosus) target strength in the North Pacific Ocean. – ICES Journal of Marine Science, 66: 258–263. In situ measurements of capelin (Mallotus villosus) target strength (TS) were collected during summer 2001–2003 near Kodiak Island in the Gulf of Alaska, using a calibrated EK500 echosounder with 38 and 120 kHz split-beam transducers. Targets were detected over dispersed, night-time aggregations using standard acoustic methods, then filtered using a quality-control algorithm to reject invalid targets. The 38 kHz-based, fitted model estimate was TS = 20 log10L− 70.3 (r2 = 0.30), where L is total length of fish. Compared with other studies, the TS-fitted model at 38 kHz was similar to that calculated from swimbladder morphology measurements from St Lawrence estuary capelin (TS = 20 log10L− 69.3), but resulted in greater estimates than models based on in situ measurements of capelin TS in the Barents Sea (TS = 19.1 log10L−74.0) and northern Atlantic Ocean (TS = 20 log10L − 73.1). The large intraspecific variability exhibited in the fitted TS – L models for this species suggests the use of TS measurements from the geographic region where the data were collected.

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

In situ measurements of orange roughy (Hoplostethus atlanticus) target strength

2007 ◽  
Vol 64 (6) ◽  
pp. 1220-1234 ◽  
Author(s):  
Roger F. Coombs ◽  
Richard Barr
Keyword(s):  
New Zealand ◽  
Standard Length ◽  
In Situ Measurements ◽  
Rate Of Change ◽  
Target Strength ◽  
Commercial Fisheries ◽  
Orange Roughy ◽  
Wide Range ◽  
Hoplostethus Atlanticus

Abstract Coombs, R. F., and Barr, R. 2007. In situ measurements of orange roughy (Hoplostethus atlanticus) target strength. – ICES Journal of Marine Science, 64: 1220–1234. Orange roughy (Hoplostethus atlanticus) support one of New Zealand's most valuable commercial fisheries, and its assessment poses many problems. Acoustic estimation using echo integration has become one of the main sources of biomass information, and for this an estimate of orange roughy target strength (TS) is needed. Its schooling characteristics together with patterns in the rate of change of phase vs. TS plots are used to identify ensembles of orange roughy targets from in situ TS data collected from a wide range of fishing areas off eastern New Zealand. The results suggest a TS of −49.3 dB for an orange roughy of 35 cm standard length.

In situ measurements of target strength with optical and model verification: a case study for blue grenadier, Macruronus novaezelandiae

2011 ◽  
Vol 68 (9) ◽  
pp. 1986-1995 ◽  
Author(s):  
Rudy J. Kloser ◽  
Tim E. Ryan ◽  
Gavin J. Macaulay ◽  
Mark E. Lewis
Keyword(s):  
Cost Effective ◽  
In Situ Measurements ◽  
Model Verification ◽  
Optical Measurements ◽  
Target Strength ◽  
Fish Length ◽  
Neutral Buoyancy ◽  
Cost Effective Method

Abstract Kloser, R. J., Ryan, T. E., Macaulay, G. J., and Lewis, M. E. 2011. In situ measurements of target strength with optical and model verification: a case study for blue grenadier, Macruronus novaezelandiae. – ICES Journal of Marine Science, 68: 1986–1995. In situ measurements of target strength (TS) of isolated fish surrounding dense schools need to be representative of the schooling fish to calculate their echo-integrated biomass. Using synchronous optical and acoustic measurements from a pelagic fishing net, the standard length (81 cm, n = 128), tilt-angle (−9°), and net-disturbed in situ TS (−34.4 dB) of Australian Macruronus novaezelandiae (blue grenadier) were confirmed at depth. In situ drift experiments of assumed undisturbed but dispersed blue grenadier recorded a mean TS of −31.8 dB (CI −33.1 to −30.9 dB) with attributed fish standard lengths of 83 cm (s.d. 7.5 cm) and weight 2.5 kg. Modelling the gasbladder showed that uncertainties in fish length, orientation, and gasbladder size could explain the differences observed. Blue grenadiers have negative buoyancy because the cavity size of their gasbladder is smaller than the volume of gas required for neutral buoyancy at depth. For the same species and length, New Zealand hoki weigh less and have smaller gasbladders than Australian blue grenadier, suggesting a conversion factor of 1.10 in length for comparative measurements. Net-attached acoustic and optical measurements indicate that model and drift in situ measurements are biased high by 2.9 and 1.0 dB, respectively. Net-attached acoustic and optical measurements are a cost-effective method of monitoring TS routinely at depth for changes in species length and weight.

scholarly journals Real-time calibration of in situ measurements of target strength

2010 ◽  
Vol 68 (3) ◽  
pp. 626-631 ◽  
Author(s):  
David N. MacLennan
Keyword(s):  
Real Time ◽  
Free Field ◽  
Forward Scattering ◽  
In Situ Measurements ◽  
Target Strength ◽  
Target Range ◽  
Standard Sphere ◽  
Time Calibration ◽  
Phase Differences

Abstract MacLennan, D. N. 2011. Real-time calibration of in situ measurements of target strength. – ICES Journal of Marine Science, 68: . The in situ measurement of target strength (TS) depends on exactly one fish being within the sampled volume. This is more likely to occur the nearer the transducer is to the fish targets. The detection rate can be improved by lowering the transducer on a cable from a stationary vessel, so decreasing the range to the observed fish. In this application, a standard sphere is commonly suspended below the transducer to provide the real-time calibration of the received signals. However, forward scattering by the sphere distorts the transmitted pulse, and equally the returning fish echoes, causing a bias in the estimated TS. Further, for a split-beam transducer, forward-scattering of the fish echo by the sphere modifies the phase differences observed between the transducer segments. This changes the apparent distribution of targets, but not the estimated TS. The biases are not large, those considered being within ±0.9 dB, and they depend on the sonar frequency, the target range, and the direction. The theory of these effects is examined, and formulae are provided for correcting the observed fish echo to that which would be received in free-field conditions, i.e. with the sphere removed.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

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