A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska
The number of harbor seals (Phoca vitulina) in Prince William Sound (PWS) has declined to approximately one-fourth of the 1975 population, and food web dynamics have been investigated as a possible factor. Stable carbon and nitrogen isotope ratios (delta13C and delta15N) are established in the prima...
Main Authors: | , |
---|---|
Format: | Conference Object |
Language: | unknown |
Published: |
NSUWorks
1999
|
Subjects: | |
Online Access: | https://nsuworks.nova.edu/occ_facpresentations/427 |
id |
ftnsoutheastern:oai:nsuworks.nova.edu:occ_facpresentations-1412 |
---|---|
record_format |
openpolar |
spelling |
ftnsoutheastern:oai:nsuworks.nova.edu:occ_facpresentations-1412 2023-05-15T15:43:41+02:00 A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska Hirons, Amy Schnell, Donald M. 1999-03-01T08:00:00Z https://nsuworks.nova.edu/occ_facpresentations/427 unknown NSUWorks https://nsuworks.nova.edu/occ_facpresentations/427 Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures Marine Biology Oceanography and Atmospheric Sciences and Meteorology conference 1999 ftnsoutheastern 2022-04-10T21:45:49Z The number of harbor seals (Phoca vitulina) in Prince William Sound (PWS) has declined to approximately one-fourth of the 1975 population, and food web dynamics have been investigated as a possible factor. Stable carbon and nitrogen isotope ratios (delta13C and delta15N) are established in the primary producers of the food chain and provide information of prey consumed at different locations and trophic levels within PWS and the adjacent Gulf of Alaska. Offshore prey have more depleted isotope values than the same species within PWS. Prey from pelagic and benthic environments have similar delta15N values but the benthos is more enriched in 13C than pelagic species. Satellite tracking data of harbor seals tagged by Alaska Department of Fish and Game personnel reveal some seals leave the sound to feed in the gulf for extended periods of time. The nutritional values of these prey relative to pelagic prey, such as herring and capelin, are unknown but likely lower. Stable isotope values from archived and modern harbor seal tissues from 1950-1996 showed that no significant difference in the delta15N values occurred during the past 47 years and this indicated no trophic shift occurred during that time. However, during that same period, a decrease in the delta13C became evident in the bone collagen of three species of phocids, including harbor seals, and otariids throughout the Bering Sea and Gulf of Alaska. That decline tracked the decline in zooplankton biomass estimates and primary productivity rates as exhibited by the stable isotope records in bowhead whale baleen. All these data in combination may indicate that the carrying capacity of the northeastern Pacific Ocean and Bering Sea has declined since the 1960s and implies serious consequences for top trophic level organisms which require high primary productivity to support the prey density necessary for successful recruitment. Conference Object Bering Sea bowhead whale harbor seal Phoca vitulina Alaska Nova Southeastern University: NSU Works Bering Sea Gulf of Alaska Pacific |
institution |
Open Polar |
collection |
Nova Southeastern University: NSU Works |
op_collection_id |
ftnsoutheastern |
language |
unknown |
topic |
Marine Biology Oceanography and Atmospheric Sciences and Meteorology |
spellingShingle |
Marine Biology Oceanography and Atmospheric Sciences and Meteorology Hirons, Amy Schnell, Donald M. A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska |
topic_facet |
Marine Biology Oceanography and Atmospheric Sciences and Meteorology |
description |
The number of harbor seals (Phoca vitulina) in Prince William Sound (PWS) has declined to approximately one-fourth of the 1975 population, and food web dynamics have been investigated as a possible factor. Stable carbon and nitrogen isotope ratios (delta13C and delta15N) are established in the primary producers of the food chain and provide information of prey consumed at different locations and trophic levels within PWS and the adjacent Gulf of Alaska. Offshore prey have more depleted isotope values than the same species within PWS. Prey from pelagic and benthic environments have similar delta15N values but the benthos is more enriched in 13C than pelagic species. Satellite tracking data of harbor seals tagged by Alaska Department of Fish and Game personnel reveal some seals leave the sound to feed in the gulf for extended periods of time. The nutritional values of these prey relative to pelagic prey, such as herring and capelin, are unknown but likely lower. Stable isotope values from archived and modern harbor seal tissues from 1950-1996 showed that no significant difference in the delta15N values occurred during the past 47 years and this indicated no trophic shift occurred during that time. However, during that same period, a decrease in the delta13C became evident in the bone collagen of three species of phocids, including harbor seals, and otariids throughout the Bering Sea and Gulf of Alaska. That decline tracked the decline in zooplankton biomass estimates and primary productivity rates as exhibited by the stable isotope records in bowhead whale baleen. All these data in combination may indicate that the carrying capacity of the northeastern Pacific Ocean and Bering Sea has declined since the 1960s and implies serious consequences for top trophic level organisms which require high primary productivity to support the prey density necessary for successful recruitment. |
format |
Conference Object |
author |
Hirons, Amy Schnell, Donald M. |
author_facet |
Hirons, Amy Schnell, Donald M. |
author_sort |
Hirons, Amy |
title |
A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska |
title_short |
A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska |
title_full |
A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska |
title_fullStr |
A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska |
title_full_unstemmed |
A Perspective on Harbor Seal Trophic Interactions in Prince William Sound and the Gulf of Alaska |
title_sort |
perspective on harbor seal trophic interactions in prince william sound and the gulf of alaska |
publisher |
NSUWorks |
publishDate |
1999 |
url |
https://nsuworks.nova.edu/occ_facpresentations/427 |
geographic |
Bering Sea Gulf of Alaska Pacific |
geographic_facet |
Bering Sea Gulf of Alaska Pacific |
genre |
Bering Sea bowhead whale harbor seal Phoca vitulina Alaska |
genre_facet |
Bering Sea bowhead whale harbor seal Phoca vitulina Alaska |
op_source |
Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures |
op_relation |
https://nsuworks.nova.edu/occ_facpresentations/427 |
_version_ |
1766377867537547264 |