Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition
We examined the digestion of hard remains of between one and four different size ranges of nine key North Sea prey taxa fed to seven captive harbour seals (Phoca vitulina). Percentage length reduction (mean 27.5%) and recovery rates (mean 42%) of experimental otoliths varied between species and were...
Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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Canadian Science Publishing
1997
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Online Access: | http://dx.doi.org/10.1139/f96-264 http://www.nrcresearchpress.com/doi/pdf/10.1139/f96-264 |
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crcansciencepubl:10.1139/f96-264 2024-09-09T20:03:31+00:00 Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition Tollit, D J Steward, M J Thompson, P M Pierce, G J Santos, M B Hughes, S 1997 http://dx.doi.org/10.1139/f96-264 http://www.nrcresearchpress.com/doi/pdf/10.1139/f96-264 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Fisheries and Aquatic Sciences volume 54, issue 1, page 105-119 ISSN 0706-652X 1205-7533 journal-article 1997 crcansciencepubl https://doi.org/10.1139/f96-264 2024-08-29T04:08:49Z We examined the digestion of hard remains of between one and four different size ranges of nine key North Sea prey taxa fed to seven captive harbour seals (Phoca vitulina). Percentage length reduction (mean 27.5%) and recovery rates (mean 42%) of experimental otoliths varied between species and were positively correlated to fish size and otolith robustness (mass/length). Mean length reduction of egested otoliths increased systematically with increasing size of ingested whiting and sandeel otoliths (p < 0.001), indicating that the size of larger fish may be underestimated. Intraspecific variation in otolith digestion was high (CV = 0.48-1.30), and to control for the artificial conditions of a captive study, external morphological features of otoliths were used to grade the degree of digestion and provide grade-specific correction factors. Bootstrap simulations were used to estimate 95% confidence intervals around correction factors and when partitioned indicated that calculation errors were in general less important than resampling errors. The application of species-, size-, and grade-specific correction factors progressively improved reconstructed estimates of prey biomass fed. As a consequence, estimates of prey size and diet composition require otoliths from faeces to be graded and more complex correction factors applied. Article in Journal/Newspaper Phoca vitulina Canadian Science Publishing Canadian Journal of Fisheries and Aquatic Sciences 54 1 105 119 |
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Open Polar |
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Canadian Science Publishing |
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crcansciencepubl |
language |
English |
description |
We examined the digestion of hard remains of between one and four different size ranges of nine key North Sea prey taxa fed to seven captive harbour seals (Phoca vitulina). Percentage length reduction (mean 27.5%) and recovery rates (mean 42%) of experimental otoliths varied between species and were positively correlated to fish size and otolith robustness (mass/length). Mean length reduction of egested otoliths increased systematically with increasing size of ingested whiting and sandeel otoliths (p < 0.001), indicating that the size of larger fish may be underestimated. Intraspecific variation in otolith digestion was high (CV = 0.48-1.30), and to control for the artificial conditions of a captive study, external morphological features of otoliths were used to grade the degree of digestion and provide grade-specific correction factors. Bootstrap simulations were used to estimate 95% confidence intervals around correction factors and when partitioned indicated that calculation errors were in general less important than resampling errors. The application of species-, size-, and grade-specific correction factors progressively improved reconstructed estimates of prey biomass fed. As a consequence, estimates of prey size and diet composition require otoliths from faeces to be graded and more complex correction factors applied. |
format |
Article in Journal/Newspaper |
author |
Tollit, D J Steward, M J Thompson, P M Pierce, G J Santos, M B Hughes, S |
spellingShingle |
Tollit, D J Steward, M J Thompson, P M Pierce, G J Santos, M B Hughes, S Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
author_facet |
Tollit, D J Steward, M J Thompson, P M Pierce, G J Santos, M B Hughes, S |
author_sort |
Tollit, D J |
title |
Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
title_short |
Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
title_full |
Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
title_fullStr |
Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
title_full_unstemmed |
Species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
title_sort |
species and size differences in the digestion of otoliths and beaks: implications for estimates of pinniped diet composition |
publisher |
Canadian Science Publishing |
publishDate |
1997 |
url |
http://dx.doi.org/10.1139/f96-264 http://www.nrcresearchpress.com/doi/pdf/10.1139/f96-264 |
genre |
Phoca vitulina |
genre_facet |
Phoca vitulina |
op_source |
Canadian Journal of Fisheries and Aquatic Sciences volume 54, issue 1, page 105-119 ISSN 0706-652X 1205-7533 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/f96-264 |
container_title |
Canadian Journal of Fisheries and Aquatic Sciences |
container_volume |
54 |
container_issue |
1 |
container_start_page |
105 |
op_container_end_page |
119 |
_version_ |
1809935458743877632 |