Pitfalls in stock discrimination by shape analysis of otolith contours
Abstract This paper focuses on artefacts that may corrupt stock discrimination by shape analysis of otolith contours, how one can examine if such artefacts are important, and how they can be avoided. The scope focuses on Fourier transforms of contour points, the linear Fisher discrimination techniqu...
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Online Access: | http://dx.doi.org/10.1093/icesjms/fsv048 http://academic.oup.com/icesjms/article-pdf/72/7/2090/31225298/fsv048.pdf |
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croxfordunivpr:10.1093/icesjms/fsv048 2024-02-11T10:01:26+01:00 Pitfalls in stock discrimination by shape analysis of otolith contours Harbitz, Alf Albert, Ole Thomas 2015 http://dx.doi.org/10.1093/icesjms/fsv048 http://academic.oup.com/icesjms/article-pdf/72/7/2090/31225298/fsv048.pdf en eng Oxford University Press (OUP) ICES Journal of Marine Science volume 72, issue 7, page 2090-2097 ISSN 1095-9289 1054-3139 Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography journal-article 2015 croxfordunivpr https://doi.org/10.1093/icesjms/fsv048 2024-01-12T10:11:14Z Abstract This paper focuses on artefacts that may corrupt stock discrimination by shape analysis of otolith contours, how one can examine if such artefacts are important, and how they can be avoided. The scope focuses on Fourier transforms of contour points, the linear Fisher discrimination technique, and success rates based on cross validation by the “leave one out at a time” technique. The “zero-score” technique is introduced as a tool to examine the importance of a possible artefact, based on the theoretical result that the probability of correct classification of any otolith from either of two identical groups is zero. If one of the identical groups is exposed to a possible influential factor, e.g. a different smoothing, a high classification rate will reveal that this factor is an important artefact. The concept of a “lasso contour” is introduced that drastically reduces the impact of smoothing and provides a non-concave shape that enables a one-dimensional representation of the contour without ambiguities. Results are illustrated by comparison between Greenland halibut (Reinhardtius hippoglossoides) otolith contours from southern Greenland and Northeast Arctic waters. The conclusion is that the probability of correct classification of locality based on the original contours is too optimistic (77–79%), while the scores based on lasso contours are insensitive to smoothing and still optimistically high (68–70%). Article in Journal/Newspaper Arctic Greenland Oxford University Press Arctic Greenland ICES Journal of Marine Science 72 7 2090 2097 |
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Oxford University Press |
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croxfordunivpr |
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English |
topic |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography |
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Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography Harbitz, Alf Albert, Ole Thomas Pitfalls in stock discrimination by shape analysis of otolith contours |
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Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography |
description |
Abstract This paper focuses on artefacts that may corrupt stock discrimination by shape analysis of otolith contours, how one can examine if such artefacts are important, and how they can be avoided. The scope focuses on Fourier transforms of contour points, the linear Fisher discrimination technique, and success rates based on cross validation by the “leave one out at a time” technique. The “zero-score” technique is introduced as a tool to examine the importance of a possible artefact, based on the theoretical result that the probability of correct classification of any otolith from either of two identical groups is zero. If one of the identical groups is exposed to a possible influential factor, e.g. a different smoothing, a high classification rate will reveal that this factor is an important artefact. The concept of a “lasso contour” is introduced that drastically reduces the impact of smoothing and provides a non-concave shape that enables a one-dimensional representation of the contour without ambiguities. Results are illustrated by comparison between Greenland halibut (Reinhardtius hippoglossoides) otolith contours from southern Greenland and Northeast Arctic waters. The conclusion is that the probability of correct classification of locality based on the original contours is too optimistic (77–79%), while the scores based on lasso contours are insensitive to smoothing and still optimistically high (68–70%). |
format |
Article in Journal/Newspaper |
author |
Harbitz, Alf Albert, Ole Thomas |
author_facet |
Harbitz, Alf Albert, Ole Thomas |
author_sort |
Harbitz, Alf |
title |
Pitfalls in stock discrimination by shape analysis of otolith contours |
title_short |
Pitfalls in stock discrimination by shape analysis of otolith contours |
title_full |
Pitfalls in stock discrimination by shape analysis of otolith contours |
title_fullStr |
Pitfalls in stock discrimination by shape analysis of otolith contours |
title_full_unstemmed |
Pitfalls in stock discrimination by shape analysis of otolith contours |
title_sort |
pitfalls in stock discrimination by shape analysis of otolith contours |
publisher |
Oxford University Press (OUP) |
publishDate |
2015 |
url |
http://dx.doi.org/10.1093/icesjms/fsv048 http://academic.oup.com/icesjms/article-pdf/72/7/2090/31225298/fsv048.pdf |
geographic |
Arctic Greenland |
geographic_facet |
Arctic Greenland |
genre |
Arctic Greenland |
genre_facet |
Arctic Greenland |
op_source |
ICES Journal of Marine Science volume 72, issue 7, page 2090-2097 ISSN 1095-9289 1054-3139 |
op_doi |
https://doi.org/10.1093/icesjms/fsv048 |
container_title |
ICES Journal of Marine Science |
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72 |
container_issue |
7 |
container_start_page |
2090 |
op_container_end_page |
2097 |
_version_ |
1790597244742795264 |