Application of two methods for determining diet of northern fur seals (Callorhinus ursinus)
Examination of hard parts recovered from scats (feces) is currently the most common method for determining the diet of pinnipeds. However, large or sharp prey remains may be spewed (regurgitated) biasing prey composition and size estimations in diet studies based on scats. Percent frequency of occur...
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ftoceandocs:oai:aquadocs.org:1834/25593 2023-05-15T18:32:52+02:00 Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) Gudmundson, Carolyn J. Zeppelin, Tonya K. Ream, Rolf R. 2006 application/pdf 445-455 http://hdl.handle.net/1834/25593 en eng http://fishbull.noaa.gov/1043/gudmundson.pdf 0090-0656 http://hdl.handle.net/1834/25593 http://aquaticcommons.org/id/eprint/8981 403 2012-08-03 19:04:30 8981 United States National Marine Fisheries Service Biology Ecology Fisheries article TRUE 2006 ftoceandocs 2023-04-06T17:02:55Z Examination of hard parts recovered from scats (feces) is currently the most common method for determining the diet of pinnipeds. However, large or sharp prey remains may be spewed (regurgitated) biasing prey composition and size estimations in diet studies based on scats. Percent frequency of occurrence (FO%) and age or size of selected prey remains recovered from northern fur seal (Callorhinus ursinus) scat (n=3444) and spew samples (n=267) collected from rookeries on St. George Island and St. Paul Island, Alaska, between 1990 and 2000 were compared to determine if a bias in prey composition and age or size estimations existed between scats and spews.Overall prey composition was similar between sample type and location, but the relative FO% of primary prey (≥5%) varied by sample type and location. Age or size estimates of walleye pollock (Theragra chalcogramma) and of two species of gonatid squids (Gonatopsis borealis and Berryteuthis magister) were significantly larger in spews than in scats. Observed differences in FO% and estimated age or size of prey species whose remains were found in scats and spews likely result from size-selective digestion of prey remains. Scats were biased toward smaller prey remains, whereas spews were biased toward larger prey remains and cephalopod beaks. The percent overlap between age classes of walleye pollock caught by the commercial trawl fishery and age classes of walleye pollock consumed by northern fur seals varied noticeably between sample types for both islands (scats: St. George=15. 5%; St. Paul=4.1%; spews: St. George=94.6%; St. Paul=89.6%). These results demonstrate that the inclusion of multiple sampling methods allows for a more accurate assessment of northern fur seal prey occurrence and prey age and size. Article in Journal/Newspaper Theragra chalcogramma Alaska Callorhinus ursinus Northern fur seal IODE-UNESCO: OceanDocs - E-Repository of Ocean Publications |
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Open Polar |
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IODE-UNESCO: OceanDocs - E-Repository of Ocean Publications |
op_collection_id |
ftoceandocs |
language |
English |
topic |
Biology Ecology Fisheries |
spellingShingle |
Biology Ecology Fisheries Gudmundson, Carolyn J. Zeppelin, Tonya K. Ream, Rolf R. Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) |
topic_facet |
Biology Ecology Fisheries |
description |
Examination of hard parts recovered from scats (feces) is currently the most common method for determining the diet of pinnipeds. However, large or sharp prey remains may be spewed (regurgitated) biasing prey composition and size estimations in diet studies based on scats. Percent frequency of occurrence (FO%) and age or size of selected prey remains recovered from northern fur seal (Callorhinus ursinus) scat (n=3444) and spew samples (n=267) collected from rookeries on St. George Island and St. Paul Island, Alaska, between 1990 and 2000 were compared to determine if a bias in prey composition and age or size estimations existed between scats and spews.Overall prey composition was similar between sample type and location, but the relative FO% of primary prey (≥5%) varied by sample type and location. Age or size estimates of walleye pollock (Theragra chalcogramma) and of two species of gonatid squids (Gonatopsis borealis and Berryteuthis magister) were significantly larger in spews than in scats. Observed differences in FO% and estimated age or size of prey species whose remains were found in scats and spews likely result from size-selective digestion of prey remains. Scats were biased toward smaller prey remains, whereas spews were biased toward larger prey remains and cephalopod beaks. The percent overlap between age classes of walleye pollock caught by the commercial trawl fishery and age classes of walleye pollock consumed by northern fur seals varied noticeably between sample types for both islands (scats: St. George=15. 5%; St. Paul=4.1%; spews: St. George=94.6%; St. Paul=89.6%). These results demonstrate that the inclusion of multiple sampling methods allows for a more accurate assessment of northern fur seal prey occurrence and prey age and size. |
format |
Article in Journal/Newspaper |
author |
Gudmundson, Carolyn J. Zeppelin, Tonya K. Ream, Rolf R. |
author_facet |
Gudmundson, Carolyn J. Zeppelin, Tonya K. Ream, Rolf R. |
author_sort |
Gudmundson, Carolyn J. |
title |
Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) |
title_short |
Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) |
title_full |
Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) |
title_fullStr |
Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) |
title_full_unstemmed |
Application of two methods for determining diet of northern fur seals (Callorhinus ursinus) |
title_sort |
application of two methods for determining diet of northern fur seals (callorhinus ursinus) |
publishDate |
2006 |
url |
http://hdl.handle.net/1834/25593 |
genre |
Theragra chalcogramma Alaska Callorhinus ursinus Northern fur seal |
genre_facet |
Theragra chalcogramma Alaska Callorhinus ursinus Northern fur seal |
op_source |
http://aquaticcommons.org/id/eprint/8981 403 2012-08-03 19:04:30 8981 United States National Marine Fisheries Service |
op_relation |
http://fishbull.noaa.gov/1043/gudmundson.pdf 0090-0656 http://hdl.handle.net/1834/25593 |
_version_ |
1766217069572915200 |