Density and Size Estimates of Cisco (Coregonus artedii) Using Analysis of Echo Peak PDF from a Single-Transducer Sonar

1987 ◽  
Vol 44 (4) ◽  
pp. 811-821 ◽  
Author(s):  
Lars G. Rudstam ◽  
Clarence S. Clay ◽  
John J. Magnuson
Keyword(s):  
Probability Density Functions ◽  
Target Strength ◽  
Fish Length ◽  
Density Functions ◽  
Density Profiles ◽  
Gill Nets ◽  
Vertical Density ◽  
Coregonus Artedii ◽  
Size Estimates

We estimated size and density of fish in three Wisconsin lakes from echo peak probability density functions (PDFs) obtained at night with a single-transducer 70-kHz echosounder. At night, cisco (Coregonus artedii) dominated the pelagic zone in all three lakes. The beam pattern effect was removed with a deconvolving filter technique. Fish size was estimated by fitting a combination of Rice PDFs to the deconvolved fish scattering PDF. Vertical density profiles and size estimates obtained acoustically corresponded to distributions and lengths of fish caught in vertical gill nets. The proportion of different size classes caught in gill nets agreed fairly well with the proportions determined acoustically. This analysis can be applied to signals from noncalibrated sonars and can be used to calibrate simultaneously obtained echo squared integration values. With calibrated sonars, target strength can be estimated in situ. For Cisco, TS = 21.9 log10L − 67.2, where TS is target strength in (decibels) and L is fish length (centimetres). The average number of Cisco in the three lakes ranged from 89 to 1551 fish/ha, corresponding to a biomass of 2–223 kg/ha. Maximum densities range from 12 to 49 fish/1000 m3.

scholarly journals Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys

2009 ◽  
Vol 66 (6) ◽  
pp. 1225-1232 ◽  
Author(s):  
Viacheslav A. Ermolchev
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Biological Data ◽  
Target Strength ◽  
Fish Length ◽  
The Barents Sea ◽  
Total Fish ◽  
Acoustic Surveys

Abstract Ermolchev, V. A., 2009. Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys. – ICES Journal of Marine Science, 66: 1225–1232. This paper presents methods for collecting acoustic and biological data, including in situ target-strength (TS) estimates of fish, with results presented for Atlantic cod (Gadus morhua) obtained from combined trawl-acoustic surveys. These include fish in the small, average, and maximum length classes, within the range 5–136 cm (total fish length, LT). The investigations were done using Simrad EK500/EK60 echosounders with split-beam transducers and special post-processing software. Based on an analysis of data collected in the Barents Sea during 1998–2007, a relationship TS = 25.2 log10(LT) − 74.8 was obtained for Atlantic cod at 38 kHz, with TS in dB and LT in centimetres. Seasonally, and for depths between 50 and 500 m, the variability in cod TS was 3.1 dB, decreasing with depth. The largest day–night difference in mean TS was in August–September, with changes as large as 1.0–1.7 dB. In the other seasons, the day–night difference was <1.0 dB.

In Situ Measurement of Solar Pond Density Profiles

1983 ◽  
Vol 105 (4) ◽  
pp. 380-382 ◽  
Author(s):  
J. Langeliers ◽  
C. G. Stojanoff
Keyword(s):  
Hydrostatic Pressure ◽  
Density Gradient ◽  
Experimental Results ◽  
Design Parameters ◽  
Density Profiles ◽  
Solar Pond ◽  
Vertical Density ◽  
The Stability ◽  
Prototype Instrument

The stability of a solar pond is critically dependent upon the maintenance of a suitable vertical density gradient, but rapid, inexpensive methods of profiling the density gradient do not presently exist. A method for obtaining in situ density profiles through measurement of hydrostatic pressure differential is described and investigated. Design parameters and experimental results are presented for a prototype instrument.

Diurnal variation in acoustic densities: why do we see less in the dark?

2004 ◽  
Vol 61 (11) ◽  
pp. 2237-2254 ◽  
Author(s):  
Vidar Hjellvik ◽  
Olav Rune Godø ◽  
Dag Tjøstheim
Keyword(s):  
Barents Sea ◽  
Dead Zone ◽  
Model Development ◽  
Demersal Fish ◽  
Target Strength ◽  
Trawl Survey ◽  
Diurnal Changes ◽  
Density Profiles ◽  
Vertical Density ◽  
Acoustic Surveys

Diurnal fluctuations in total integrated echo abundance and in vertical density profiles were examined using data from the Norwegian combined acoustic and bottom-trawl survey for demersal fish during winter in the Barents Sea. The total echo abundance was about 40%–50% higher at day than at night. An unknown amount of fish was lost close to the seabed in the acoustic dead zone, but the systematic changes in the near-bottom vertical density profiles did not indicate that migration in and out of the dead zone was the major reason for the large diurnal differences in echo abundance. A more plausible explanation could be that diurnal changes in fish behaviour affect the mean acoustic target strength. Based on the present study, we recommend that the time series of acoustic surveys should be re analysed, taking the diurnal bias into account. Any comparison of the fish densities indicated by trawl and acoustic surveys will suffer if this bias is not corrected. We believe that model development utilizing this type of information is crucial for future ecosystem-based monitoring.

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.

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 Application of in situ target-strength estimations in lakes: examples from rainbow-smelt surveys in Lakes Erie and Champlain

2003 ◽  
Vol 60 (3) ◽  
pp. 500-507 ◽  
Author(s):  
L.G Rudstam ◽  
S.L Parker ◽  
D.W Einhouse ◽  
L.D Witzel ◽  
D.M Warner ◽  
...  
Keyword(s):  
Lake Erie ◽  
Growing Season ◽  
Target Strength ◽  
Fish Length ◽  
Osmerus Mordax ◽  
Rainbow Smelt ◽  
Acoustic Data ◽  
Size Groups ◽  
High Fish

Abstract Acoustic abundance of fish depends directly on the target strength (TS) of the fish surveyed. We analyzed 70 and 120 kHz acoustic data from two lakes with abundant rainbow-smelt (Osmerus mordax) populations. Using repeated surveys through the summer growing season, we derived a relationship between TS (dB) and fish length L (cm) at 120 kHz (TS = 19.9 log10 L − 67.8). Values for 70 kHz were similar. In situ TS increased with fish density, indicating a bias from accepting multiple targets at high fish densities. Correcting for this bias increased estimates of smelt abundance by up to 18% in Lake Erie and up to 100% in Lake Champlain. Multiple modes in the TS distributions observed for older fish do not reflect different size groups, as the same modes can be observed from measurements from a single fish. Smelt released gas bubbles during the evening ascent, and these bubbles had TS (−60 to −58 dB) within the range of TS observed from the fish. Gas-bubble release occurred mostly during the migration. Conducting surveys after the ascent is completed will decrease bias associated with counting bubbles as fish.

A new radiometric instrument for in situ measurements of physical sediment properties

2009 ◽  
Vol 60 (7) ◽  
pp. 727 ◽  
Author(s):  
W. Jacobs ◽  
M. Eelkema ◽  
H. Limburg ◽  
J. C. Winterwerp
Keyword(s):  
Cost Effective ◽  
Sample Collection ◽  
Sediment Composition ◽  
Density Profiles ◽  
Sediment Properties ◽  
Sediment Bed ◽  
New Instrument ◽  
Vertical Density ◽  
Practical Tool

Information on the sedimentological composition of sediment beds in marine wetlands is important for the study of the complicated interactions between physical, biological and chemical processes. In situ soil sample collection and subsequent laboratory analyses using traditional methods is rather time consuming. The present paper presents the Medusa (Multi Detector system for Underwater Sediment Activity) RhoC system. ‘Rho’ refers to density and ‘C’ to the activity concentration of the decaying isotopes adhered to the sediments. The new instrument directly translates (the attenuation of) natural radioactivity to sedimentological data concerning the depth-averaged sediment composition and vertical density profiles of the upper 15 cm of the sediment bed. The accuracy and applicability of the instrument were assessed to illustrate its potential and limitations. Results from a field campaign on several intertidal flats and from similar measurements in the laboratory for controlled circumstances were compared with data obtained by traditional analyses. The instrument generates accurate results for the depth-averaged sediment composition. Vertical density profiles are also well represented by the RhoC after smoothing and correcting the data for partly saturated soils. Thus, Medusa RhoC is a useful and practical tool to provide accurate sedimentological data in a fast and cost-effective way. The combination of sedimentological relations with the data obtained by RhoC further increases the applicability of the new instrument.

scholarly journals Characterizing uncertainty in target-strength measurements of a deepwater fish: orange roughy (Hoplostethus atlanticus)

2003 ◽  
Vol 60 (3) ◽  
pp. 516-523 ◽  
Author(s):  
R.J Kloser ◽  
J.K Horne
Keyword(s):  
Active Avoidance ◽  
Target Selection ◽  
Target Strength ◽  
Wax Ester ◽  
Fish Length ◽  
Orange Roughy ◽  
Single Target ◽  
Species Specific ◽  
Hoplostethus Atlanticus

Abstract The variability of ensemble 38 kHz, target-strength (TS38) estimates for orange roughy (Hoplostethus atlanticus) (4.9 dB, factor of 3.1) in deep water (>600 m) limits the use of echo integration for absolute-biomass estimates. Orange roughy are high in oil content, have a wax-ester swimbladder, and show an active-avoidance response to sampling gear. The interpretations of ensemble, in situ target strengths of orange roughy (range 〈TS38〉=−52.9 to −51.0 dB for standard fish length 〈SL〉 = 35 cm) are lower than previous model and surface-based measurements (〈TS38〉 = −48 dB, SL = 35 cm). In situ TS measurements from individuals on the periphery of dense schools were processed to minimize uncertainties from single-target selection criteria, species composition, and active avoidance. Video and acoustic-tracking data quantified the variability in TS measurements arising from the variability in fish orientation. Multi-frequency acoustics and fish tracking are used to quantify in situ TS variability due to species identification and fish density. The Kirchhoff-ray-mode backscatter model was used to illustrate the sensitivity of species-specific backscatter to assumptions of tilt-angle and material properties (density and sound-speed contrasts). We conclude that a remaining source of uncertainty for in situ TS measurements is the assumption that dispersed targets are representative of the survey population.

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