Acoustic species identification of schooling fish / Korneliussen, Rolf J.

Public ISBD Faire une suggestion d'achat Titre : Acoustic species identification of schooling fish Type de document : texte imprimé Auteurs : Korneliussen, Rolf J., Auteur Importance : pp. 1111-1118 Langues : Anglais (eng) Index. décimale : 508 Voyages et relevés scientifiques. Histoire naturelle Résumé : The development of methods for the acoustic identification of fish is a long-term objective aimed at reducing uncertainty in acoustic-survey estimates. The relative frequency response r(f) measured simultaneously at several frequencies is one of the main acoustic features that characterize the targets, but the relationship between nearest neighbours, school morphology, and environmental and geographical data are also important characteristics in this context. The number of acoustic categories that can be separated with a high spatial resolution is limited by the stochastic nature of the measurements. Because the acoustic categorization of larger ensembles is more reliable than for single targets, spatial smoothing of the backscattering within the school boundaries before that process allows the separation of more categories than is possible with the raw, highly resolved data. Using the mean r(f) of an entire school gives even more reliable categorization, but determining whether or not the school is monospecific sets a new challenge. This problem is evaluated here. The methods are tested and verified. Identification of acoustic categories with similar acoustic properties is done for schooling fish, although the results have limited spatial resolution. The reliability of the categorization is further improved when knowledge of school morphology and geographical distribution of the species are taken into account. Acoustic species identification of schooling fish [texte imprimé] / Korneliussen, Rolf J., Auteur . - [s.d.] . - pp. 1111-1118. Langues : Anglais (eng) Index. décimale : 508 Voyages et relevés scientifiques. Histoire naturelle Résumé : The development of methods for the acoustic identification of fish is a long-term objective aimed at reducing uncertainty in acoustic-survey estimates. The relative frequency response r(f) measured simultaneously at several frequencies is one of the main acoustic features that characterize the targets, but the relationship between nearest neighbours, school morphology, and environmental and geographical data are also important characteristics in this context. The number of acoustic categories that can be separated with a high spatial resolution is limited by the stochastic nature of the measurements. Because the acoustic categorization of larger ensembles is more reliable than for single targets, spatial smoothing of the backscattering within the school boundaries before that process allows the separation of more categories than is possible with the raw, highly resolved data. Using the mean r(f) of an entire school gives even more reliable categorization, but determining whether or not the school is monospecific sets a new challenge. This problem is evaluated here. The methods are tested and verified. Identification of acoustic categories with similar acoustic properties is done for schooling fish, although the results have limited spatial resolution. The reliability of the categorization is further improved when knowledge of school morphology and geographical distribution of the species are taken into account.

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Combining multibeam-sonar and multifrequency-echosounder data / Korneliussen, Rolf J.

Public ISBD Faire une suggestion d'achat Titre : Combining multibeam-sonar and multifrequency-echosounder data : examples of the analysis and imaging of large euphausiid schools Type de document : texte imprimé Auteurs : Korneliussen, Rolf J., Auteur Importance : pp. 991-997 Langues : Anglais (eng) Index. décimale : 508 Voyages et relevés scientifiques. Histoire naturelle Résumé : The first high-resolution, quantitative, multibeam sonar (Simrad MS70) ever developed was mounted in a keel of RV "G. O. Sars" with port-orientated beams. Each ping samples a volume of 60 horizontally x 45 vertically with 500 beams, which is often enough to insonify a complete school of fish or zooplankton. The large amount of resulting data is efficiently preprocessed with automatic, real-time detections of school candidates; these are accepted or rejected during post-processing. The system was used on the continental shelf near the Subantarctic island of South Georgia to study Antarctic krill (Euphausia superba), and some of the detected schools were immediately sampled with a six-frequency echosounder (Simrad EK60), then trawled with various nets to verify the target species and their size composition. For schools acoustically categorized as euphausiids, data from the two acoustic systems were used to estimate the school morp ho metrics and the krill size distributions. The principal objectives of this study were to explore the potential of combining data from a multibeam sonar, multifrequency echosounders, and nets, and to describe the efficient processing methods and software that facilitate the multi-instrument analyses. Three-dimensional morphometrics based on the MS70 data were consistent with corresponding two-dimensional morphometrics based on the echosounder data and could be used to improve the acoustic classifications of taxa or species. Additionally, automatic preprocessing and integration of data from different sources into the same user interface allowed efficient exploration and interpretation of all the acoustic data. Combining multibeam-sonar and multifrequency-echosounder data : examples of the analysis and imaging of large euphausiid schools [texte imprimé] / Korneliussen, Rolf J., Auteur . - [s.d.] . - pp. 991-997. Langues : Anglais (eng) Index. décimale : 508 Voyages et relevés scientifiques. Histoire naturelle Résumé : The first high-resolution, quantitative, multibeam sonar (Simrad MS70) ever developed was mounted in a keel of RV "G. O. Sars" with port-orientated beams. Each ping samples a volume of 60 horizontally x 45 vertically with 500 beams, which is often enough to insonify a complete school of fish or zooplankton. The large amount of resulting data is efficiently preprocessed with automatic, real-time detections of school candidates; these are accepted or rejected during post-processing. The system was used on the continental shelf near the Subantarctic island of South Georgia to study Antarctic krill (Euphausia superba), and some of the detected schools were immediately sampled with a six-frequency echosounder (Simrad EK60), then trawled with various nets to verify the target species and their size composition. For schools acoustically categorized as euphausiids, data from the two acoustic systems were used to estimate the school morp ho metrics and the krill size distributions. The principal objectives of this study were to explore the potential of combining data from a multibeam sonar, multifrequency echosounders, and nets, and to describe the efficient processing methods and software that facilitate the multi-instrument analyses. Three-dimensional morphometrics based on the MS70 data were consistent with corresponding two-dimensional morphometrics based on the echosounder data and could be used to improve the acoustic classifications of taxa or species. Additionally, automatic preprocessing and integration of data from different sources into the same user interface allowed efficient exploration and interpretation of all the acoustic data.

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