Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999
Lengths of walleye pollock (Theragra chalcogramma) consumed by Steller sea lions (Eumetopias jubatus) were estimated by using allometric regressions applied to seven diagnostic cranial structures recovered from 531 scats collected in Southeast Alaska between 1994 and 1999. Only elements in good and...
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ftaquaticcommons:oai:generic.eprints.org:15079 2023-05-15T15:43:58+02:00 Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 Tollit, Dominic J. Heaslip, Susan G. Trites, Andrew W. 2004 application/pdf http://aquaticcommons.org/15079/ http://fishbull.noaa.gov/1023/tollit2.pdf http://aquaticcommons.org/15079/1/tollit2.pdf en eng http://aquaticcommons.org/15079/1/tollit2.pdf Tollit, Dominic J. and Heaslip, Susan G. and Trites, Andrew W. (2004) Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999. Fishery Bulletin, 102(3), pp. 522-532. Ecology Fisheries Article PeerReviewed 2004 ftaquaticcommons 2020-02-27T09:26:46Z Lengths of walleye pollock (Theragra chalcogramma) consumed by Steller sea lions (Eumetopias jubatus) were estimated by using allometric regressions applied to seven diagnostic cranial structures recovered from 531 scats collected in Southeast Alaska between 1994 and 1999. Only elements in good and fair condition were selected. Selected structural measurements were corrected for loss of size due to erosion by using experimentally derived condition-specific digestion correction factors. Correcting for digestion increased the estimated length of fish consumed by 23%, and the average mass of fish consumed by 88%. Mean corrected fork length (FL) of pollock consumed was 42.4 ±11.6 cm (range=10.0−78.1 cm, n=909). Adult pollock (FL>45.0 cm) occurred more frequently in scats collected from rookeries along the open ocean coastline of Southeast Alaska during June and July (74% adults, mean FL=48.4 cm) than they did in scats from haul-outs located in inside waters between October and May (51% adults, mean FL=38.4 cm). Overall, the contribution of juvenile pollock (≤20 cm) to the sea lion diet was insignificant; whereas adults contributed 44% to the diet by number and 74% by mass. On average, larger pollock were eaten in summer at rookeries throughout Southeast Alaska than at rookeries in the Gulf of Alaska and the Bering Sea. Overall it appears that Steller sea lions are capable of consuming a wide size range of pollock, and the bulk of fish fall between 20 and 60 cm. The use of cranial hard parts other than otoliths and the application of digestion correction factors are fundamental to correctly estimating the sizes of prey consumed by sea lions and determining the extent that these sizes overlap with the sizes of pollock caught by commercial fisheries. Article in Journal/Newspaper Bering Sea Theragra chalcogramma Alaska International Association of Aquatic and Marine Science Libraries and Information Centers (IAMSLIC): Aquatic Commons Bering Sea Gulf of Alaska |
institution |
Open Polar |
collection |
International Association of Aquatic and Marine Science Libraries and Information Centers (IAMSLIC): Aquatic Commons |
op_collection_id |
ftaquaticcommons |
language |
English |
topic |
Ecology Fisheries |
spellingShingle |
Ecology Fisheries Tollit, Dominic J. Heaslip, Susan G. Trites, Andrew W. Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 |
topic_facet |
Ecology Fisheries |
description |
Lengths of walleye pollock (Theragra chalcogramma) consumed by Steller sea lions (Eumetopias jubatus) were estimated by using allometric regressions applied to seven diagnostic cranial structures recovered from 531 scats collected in Southeast Alaska between 1994 and 1999. Only elements in good and fair condition were selected. Selected structural measurements were corrected for loss of size due to erosion by using experimentally derived condition-specific digestion correction factors. Correcting for digestion increased the estimated length of fish consumed by 23%, and the average mass of fish consumed by 88%. Mean corrected fork length (FL) of pollock consumed was 42.4 ±11.6 cm (range=10.0−78.1 cm, n=909). Adult pollock (FL>45.0 cm) occurred more frequently in scats collected from rookeries along the open ocean coastline of Southeast Alaska during June and July (74% adults, mean FL=48.4 cm) than they did in scats from haul-outs located in inside waters between October and May (51% adults, mean FL=38.4 cm). Overall, the contribution of juvenile pollock (≤20 cm) to the sea lion diet was insignificant; whereas adults contributed 44% to the diet by number and 74% by mass. On average, larger pollock were eaten in summer at rookeries throughout Southeast Alaska than at rookeries in the Gulf of Alaska and the Bering Sea. Overall it appears that Steller sea lions are capable of consuming a wide size range of pollock, and the bulk of fish fall between 20 and 60 cm. The use of cranial hard parts other than otoliths and the application of digestion correction factors are fundamental to correctly estimating the sizes of prey consumed by sea lions and determining the extent that these sizes overlap with the sizes of pollock caught by commercial fisheries. |
format |
Article in Journal/Newspaper |
author |
Tollit, Dominic J. Heaslip, Susan G. Trites, Andrew W. |
author_facet |
Tollit, Dominic J. Heaslip, Susan G. Trites, Andrew W. |
author_sort |
Tollit, Dominic J. |
title |
Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 |
title_short |
Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 |
title_full |
Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 |
title_fullStr |
Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 |
title_full_unstemmed |
Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999 |
title_sort |
sizes of walleye pollock (theragra chalcogramma) consumed by the eastern stock of steller sea lions (eumetopias jubatus) in southeast alaska from 1994 to 1999 |
publishDate |
2004 |
url |
http://aquaticcommons.org/15079/ http://fishbull.noaa.gov/1023/tollit2.pdf http://aquaticcommons.org/15079/1/tollit2.pdf |
geographic |
Bering Sea Gulf of Alaska |
geographic_facet |
Bering Sea Gulf of Alaska |
genre |
Bering Sea Theragra chalcogramma Alaska |
genre_facet |
Bering Sea Theragra chalcogramma Alaska |
op_relation |
http://aquaticcommons.org/15079/1/tollit2.pdf Tollit, Dominic J. and Heaslip, Susan G. and Trites, Andrew W. (2004) Sizes of walleye pollock (Theragra chalcogramma) consumed by the eastern stock of Steller sea lions (Eumetopias jubatus) in Southeast Alaska from 1994 to 1999. Fishery Bulletin, 102(3), pp. 522-532. |
_version_ |
1766378184966668288 |