The target strengths of fish

Haslett, R.W.G.

doi:10.1016/0022-460x(69)90026-1

Cited by 14 publications

(6 citation statements)

References 14 publications

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“…Estimates of the target strengths of siphonophores by Pickwell based on measured dimensions are acceptable at frequencies below resonance, but the resonant cross-section is probably over-estimated, since the damping factor for the pneumatophore will be greater than the assumed 'free bubble' value. Acoustic scattering from larval fish can probably be calculated by scaling from measurements on larger fish (Haslett, 1969).…”

Section: Target Strengths Of Planktonic Organismsmentioning

confidence: 99%

Comparison of the acoustic and biological sampling of the sonic scattering layers: R.R.S. ‘Discovery’ SOND Cruise, 1965

McCartney¹

1976

J. Mar. Biol. Ass.

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The acoustic measurements made during the SOND cruise are presented in the form of vertical profiles of relative scattering coefficient at day and night and its time dependence over sunrise and sunset for the four echo-sounders used. These profiles are compared with the scattering which is calculated would be returned from the vertical distributions of biological samples reported by other workers, but particularly from the distribution ofswimbladder fish analysed by Badcock. The similarities between the calculated and measured profiles support the assumption that swimbladder fish dominate the scattering due to their high target strengths, particularly at frequencies up to and including 36 kHz. By correlating fish sizes, daytime depth, migration behaviour and acoustic scattering several of the layers may be tentatively attributed to particular species. A calibrated echo-sounder in the frequency range up to 36 kHz is size selective, but can nevertheless be useful for looking at broad distributional features. However, because the numerically more abundant small planktonic animals are inadequately represented by the sounder the records are little more than a guide to net sampling programmes.

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Section: Target Strengths Of Planktonic Organismsmentioning

confidence: 99%

Comparison of the acoustic and biological sampling of the sonic scattering layers: R.R.S. ‘Discovery’ SOND Cruise, 1965

McCartney¹

1976

J. Mar. Biol. Ass.

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“…In this situation, individuals on the periphery of an aggregation are often used to tabulate a length-frequency distribution of the group. This frequency distribution is used in a regression equation to estimate lengths and densities of organisms within an aggregation (e.g., Haslett 1969;Holliday and Pieper 1980;Ehrenberg et al 1981). This approach assumes that the type and length-frequency distribution of organisms at the periphery matches that of individuals within the aggregation.…”

Section: Acoustic Constraintsmentioning

confidence: 99%

Sonar systems and aquatic organisms: matching equipment and model parameters

Horne¹,

Clay²

1998

Can. J. Fish. Aquat. Sci.

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Acoustic technology is an accepted and important component of aquatic research and resource management. Despite the widespread use of echosounders, few guidelines aid in the choice of appropriate sonar system parameters for acoustic surveys. Choice of acoustic carrier frequency is analogous to the choice of spotlight colour used to illuminate a painting. Three primary biological factors influence the scattering of sound by aquatic organisms: swimbladder presence, organism length, and organism behaviour. We illustrate the influence of these factors on the amplitude of backscattered echoes using a Kirchhoff-ray mode scattering model to quantify fish and zooplankton backscatter as a function of carrier frequency, fish length, and swimbladder aspect. Model results illustrate that echo amplitudes from aquatic organisms are largely dependent on the presence or absence of a swimbladder. Target strengths generally increase with increasing carrier frequency and organism length. Swimbladder angle relative to the incident sound wave affects scattering amplitudes at all frequencies. Measurements of backscatter from swimbladdered fish are relatively robust when the ratio of fish length to acoustic frequency wavelength ranges between 2 and 10. As fish length to frequency wavelength ratios increase, echo amplitudes become more dependent on aspect and peak when the swimbladder is perpendicular to the acoustic wavefront.

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“…Ex situ measurements of tethered fish include those conducted by Jones and Pearce (1958), Haslett (1969), Diercks and Goldsberry (1970), Love (1969Love ( , 1970Love ( , 1971, Nakken and Olson (1977), Miyanohana et al (1990), and Benoit-Bird and Au (2001). Although most of these measurements were performed at single frequencies and at a limited number of angles of orientation (mostly dorsal), they were performed on a variety of species of different sizes and demonstrate complicated variability that is dependent upon morphology, orientation and acoustic wavelength.…”

Section: Introductionmentioning

confidence: 99%