Consistent melanophore spot patterns allow long‐term individual recognition of Atlantic salmon Salmo salar

The present study shows that permanent melanophore spot patterns in Atlantic salmon Salmo salar make it possible to use images of the operculum to keep track of individual fish over extended periods of their life history. Post‐smolt S. salar ( n = 246) were initially photographed at an average mass...

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Bibliographic Details
Published in:Journal of Fish Biology
Main Authors: Stien, L. H., Nilsson, J., Bui, S., Fosseidengen, J. E., Kristiansen, T. S., Øverli, Ø., Folkedal, O.
Other Authors: Norges Forskningsråd
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2017
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Online Access:http://dx.doi.org/10.1111/jfb.13491
https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjfb.13491
https://onlinelibrary.wiley.com/doi/pdf/10.1111/jfb.13491
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Summary:The present study shows that permanent melanophore spot patterns in Atlantic salmon Salmo salar make it possible to use images of the operculum to keep track of individual fish over extended periods of their life history. Post‐smolt S. salar ( n = 246) were initially photographed at an average mass of 98 g and again 10 months later after rearing in a sea cage, at an average mass of 3088 g. Spots that were present initially remained and were the most overt (largest) 10 months later, while new and less overt spots had developed. Visual recognition of spot size and position showed that fish with at least four initial spots were relatively easy to identify, while identifying fish with less than four spots could be challenging. An automatic image analysis method was developed and shows potential for fast match processing of large numbers of fish. The current findings promote visual recognition of opercular spots as a welfare‐friendly alternative to tagging in experiments involving salmonid fishes.