Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska
Thesis (M.S.) University of Alaska Fairbanks, 2019 Increases in the humpback whale (Megaptera novaeangliae) population have generated considerable interest in understanding the foraging habits of these large marine predators in the Gulf of Alaska. Globally, humpback whales are classified as generali...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/10902 2023-05-15T16:35:55+02:00 Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska Kosma, Madison M. McPhee, Megan V. Straley, Janice M. Szabo, Andrew R. Wooller, Matthew J. 2019-12 http://hdl.handle.net/11122/10902 en_US eng http://hdl.handle.net/11122/10902 Department of Fisheries humpback whale food behavior Southeast Alaska Thesis ms 2019 ftunivalaska 2023-02-23T21:37:35Z Thesis (M.S.) University of Alaska Fairbanks, 2019 Increases in the humpback whale (Megaptera novaeangliae) population have generated considerable interest in understanding the foraging habits of these large marine predators in the Gulf of Alaska. Globally, humpback whales are classified as generalist predators but are known to exhibit localized differences in diet. Intensified predation pressure is of particular concern to resource managers, who have observed whales feeding at juvenile hatchery salmon release sites in Southeast Alaska. We assessed the diets and behavioral tactics of humpback whales foraging near Hidden Falls Hatchery release sites (in Chatham Strait, 2016 to 2018) to better understand their predatory effects on juvenile hatchery-reared salmon. We used skin biopsies, prey sampling, and stable isotope analysis to estimate whales' diet composition. Aerial footage and photographic sequences were used to assess the foraging tactics used on this prey source. We observed three individual whales repeatedly feeding on juvenile hatchery-reared salmon, and we were able to sample them multiple times over a period spanning shifts in diet. Overall, the diets of these whales were higher trophically than other humpback whales foraging in the area, even before feeding on juvenile hatchery salmon started. These hatchery-feeding whales may be generally more piscivorous than other whales, which focused on planktivorous prey. Our repeat sampling, in conjunction with scheduled introductions of a novel prey source, provided a semi-controlled feeding experiment that allowed for incorporation and turnover rate estimates from humpback whale tissue in a way that was not previously possible for large, free-ranging cetaceans. Finally, during the course of this study we discovered an undescribed feeding tactic employed by hatchery-associated whales. We observed the use of solo bubble-nets to initially corral prey, followed by calculated movements to establish a secondary boundary with the pectoral fins that further ... Thesis Humpback Whale Megaptera novaeangliae Alaska University of Alaska: ScholarWorks@UA Corral ENVELOPE(-62.950,-62.950,-64.900,-64.900) Fairbanks Gulf of Alaska |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
humpback whale food behavior Southeast Alaska |
spellingShingle |
humpback whale food behavior Southeast Alaska Kosma, Madison M. Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska |
topic_facet |
humpback whale food behavior Southeast Alaska |
description |
Thesis (M.S.) University of Alaska Fairbanks, 2019 Increases in the humpback whale (Megaptera novaeangliae) population have generated considerable interest in understanding the foraging habits of these large marine predators in the Gulf of Alaska. Globally, humpback whales are classified as generalist predators but are known to exhibit localized differences in diet. Intensified predation pressure is of particular concern to resource managers, who have observed whales feeding at juvenile hatchery salmon release sites in Southeast Alaska. We assessed the diets and behavioral tactics of humpback whales foraging near Hidden Falls Hatchery release sites (in Chatham Strait, 2016 to 2018) to better understand their predatory effects on juvenile hatchery-reared salmon. We used skin biopsies, prey sampling, and stable isotope analysis to estimate whales' diet composition. Aerial footage and photographic sequences were used to assess the foraging tactics used on this prey source. We observed three individual whales repeatedly feeding on juvenile hatchery-reared salmon, and we were able to sample them multiple times over a period spanning shifts in diet. Overall, the diets of these whales were higher trophically than other humpback whales foraging in the area, even before feeding on juvenile hatchery salmon started. These hatchery-feeding whales may be generally more piscivorous than other whales, which focused on planktivorous prey. Our repeat sampling, in conjunction with scheduled introductions of a novel prey source, provided a semi-controlled feeding experiment that allowed for incorporation and turnover rate estimates from humpback whale tissue in a way that was not previously possible for large, free-ranging cetaceans. Finally, during the course of this study we discovered an undescribed feeding tactic employed by hatchery-associated whales. We observed the use of solo bubble-nets to initially corral prey, followed by calculated movements to establish a secondary boundary with the pectoral fins that further ... |
author2 |
McPhee, Megan V. Straley, Janice M. Szabo, Andrew R. Wooller, Matthew J. |
format |
Thesis |
author |
Kosma, Madison M. |
author_facet |
Kosma, Madison M. |
author_sort |
Kosma, Madison M. |
title |
Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska |
title_short |
Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska |
title_full |
Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska |
title_fullStr |
Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska |
title_full_unstemmed |
Foraging tactics of humpback whales feeding near salmon hatchery-release sites in Southeast Alaska |
title_sort |
foraging tactics of humpback whales feeding near salmon hatchery-release sites in southeast alaska |
publishDate |
2019 |
url |
http://hdl.handle.net/11122/10902 |
long_lat |
ENVELOPE(-62.950,-62.950,-64.900,-64.900) |
geographic |
Corral Fairbanks Gulf of Alaska |
geographic_facet |
Corral Fairbanks Gulf of Alaska |
genre |
Humpback Whale Megaptera novaeangliae Alaska |
genre_facet |
Humpback Whale Megaptera novaeangliae Alaska |
op_relation |
http://hdl.handle.net/11122/10902 Department of Fisheries |
_version_ |
1766026219399151616 |