Multiple-Frequency Acoustic Backscattering and Zooplankton Aggregations in the Inner Scotian Shelf Basins

Cochrane, N. A.; Sameoto, D. D.; Herman, AW; Neilson, Janet L.

doi:10.1139/f91-046

Cited by 55 publications

(22 citation statements)

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“…Our study is one of the first to examine potential target strength differences between several fish species having comparable length distributions and anatomical features. In previous studies, frequency-dependent scattering has been used to identify and discriminate krill and zooplankton from other scatterers such as fish (Cochrane et al, 1991;Madureira et al, 1993;Kang et al, 2002). Kloser et al (2002) successfully used frequency-dependent scattering with three frequencies (12 kHz, 38 kHz, and 120 kHz) to isolate echoes from different classes of scatterers: fish with large swimbladders (Macrourids and Mourids), fish with small swimbladders (Myctophids), and orange roughy (Hoplostethus atlanticus, a species with a wax-ester filled swimbladder).…”

Section: Discussionmentioning

confidence: 99%

Potential acoustic discrimination within boreal fish assemblages

Gauthier

Horne

2004

ICES Journal of Marine Science

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2004. Potential acoustic discrimination within boreal fish assemblages. e ICES Journal of Marine Science, 61: 836e845.Differences in the acoustic characteristics of forage fish species in the Gulf of Alaska and the Bering Sea were examined using Kirchhoff ray-mode (KRM) backscatter models. Our goal was to identify species-specific characteristics and metrics that facilitate the discrimination of species using acoustic techniques. Five fish species were analyzed: capelin (Mallotus villosus), Pacific herring (Clupea pallasii), walleye pollock (Theragra chalcogramma), Atka mackerel (Pleurogrammus monopterygius), and eulachon (Thaleichthys pacificus). Backscatter amplitude differences exist among these species, especially between swimbladdered and non-swimbladdered fish. Echo intensities were variable within and among species. The effect of morphological variability was indexed using the ratio of the Reducedscattering length (RSL) standard deviation over its mean. Morphological variability was low only at fish length to acoustic wavelength ratios less than eight. Target strength differences between pairs of carrier frequencies (ranging from 12 kHz to 200 kHz) differed among species, and were dependent on fish size and body orientation. Frequency differencing successfully discriminated between fish species but the choice of frequency to maximize target strength differences was not consistent among species pairs. Frequencydependent, backscatter model predictions facilitate comparison of target strength differences prior to acoustic data collection.

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Section: Discussionmentioning

confidence: 99%

Potential acoustic discrimination within boreal fish assemblages

Gauthier

Horne

2004

ICES Journal of Marine Science

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“…If the more precise figures of Meganyctiphanes abundance that are now attainable (e.g. NICOL 1986;COCHRANE & al. 1991) are combined (i.e.…”

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Meganyctiphanes norvegica(M. sars) (Euphausiacea) a voracious predator onCalanus, other copepods, and ctenophores, in oslofjorden, southern Norway

Beyer

1992

Sarsia

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SARSIA BEYER, FREDRIK 1992 12 31. Meganyctiphanes norvegica (M. SARS) (Euphausiacea) avoracious predator on Calanus, other copepods, and ctenophores, in Oslofjorden, In zooplankton samples collected by means of vertical Nansen net hauls for the purpose of studying long-term changes in Oslofjorden, many injured specimens of Calanus were found. These had exactly the same appearance as some Calanus that were found .in Meganyctiphanes 'baskets'. It is concluded that feeding activity of Meganyctiphanes was the cause for the occurrence in the samples of injured Calanus and other copepods, "which had evidently been discarded or lost by the predators while in the net or immediately in front of it. Calanus was the main food of Meganyctiphanes in the area at that time followed by smaller copepods. Specimens that had been attacked by Meganyctiphanes constituted a significant percentage of the total number of copepods. These important relationships would not have been disclosed by examination of Meganyctiphanes stomachs alone. It is hoped that the photographs presented in this paper will prove useful to other planktologists working in waters with numerous Meganyctiphanes. With regard to fisheries biology, an overall beneficial effect of an abundant Meganyctiphanes population is not obvious since the Meganyctiphanes may consume more potential fish food than they produce. By eating Pleurobrachia, however, Meganyctiphanes may also save copepods and fish larvae from being eaten by those.

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“…1. The Batfish vehicle showing artificial lights installed above the O P r strength inversion were calculated using the statistically oriented high pass fluid cylinder models as described by Cochrane et al (1991). In this case an orientational standard deviation of 5' and a mean length of 2.8 cm for Meganyctiphanes norvegica was used in the acoustical model (Sameoto et al 1993).…”

Section: Sampling Area and Methodsmentioning

confidence: 99%

Detection and abundance estimation of euphausiids using an optical plankton counter

Herman¹,

Cochrane²,

Sameoto³

1993

Mar. Ecol. Prog. Ser.

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An optical plankton counter (OPC) mounted on a towed Batfish vehicle was used to detect and estimate the abundance of euphausiids in the Emerald and La Have Basins of the Scotian Shelf, northwest Atlantic Ocean. Euphausiids (Meganyctiphanes norvegica and Thysanoessa inermis) were identified from their characteristic diameter distributions measured by the OPC. The diameter distributions containing euphausiid peaks were compared to several depth strata known to contain these animals. The depth strata containing euphausiids were established from acoust~cal tows made on the same cruise and the identification of animals was accomplished by sampling these acoustical layers with the BIONESS net sampler. The die1 migration patterns of the euphausiids were also identified from these diameter distributions. Euphausiid reaction to artificial lights mounted on Batfish and BIONESS showed increases in abundance estimates by a factor of 2 x and 50x respectively. Experiments with artificial lights mounted on a remotely operated vehicle and camera platforms are also described. An artificial light mounted on a towed Batfish resulted in a distinct increase in euphausiid abundance estimates as measured by the OPC. Abundance estimates from the OPC are also compared to results from acoustical tows and showed agreement to within a factor of 2 and better.

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Multiple-Frequency Acoustic Backscattering and Zooplankton Aggregations in the Inner Scotian Shelf Basins

Cited by 55 publications

References 0 publications

Potential acoustic discrimination within boreal fish assemblages

Potential acoustic discrimination within boreal fish assemblages

Meganyctiphanes norvegica(M. sars) (Euphausiacea) a voracious predator onCalanus, other copepods, and ctenophores, in oslofjorden, southern Norway

Detection and abundance estimation of euphausiids using an optical plankton counter

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