Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis
Understanding the diet of deep-diving predators can provide essential insight to the trophic structure of the mesopelagic ecosystem. Comprehensive population-level diet estimates are exceptionally difficult to obtain for elusive marine predators due to the logistical challenges involved in observing...
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doaj-1ead02ac7a2b43a4b29a04e59d3306212020-11-25T02:11:08ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452018-11-01510.3389/fmars.2018.00430406373Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature AnalysisChandra Goetsch0Melinda G. Conners1Melinda G. Conners2Suzanne M. Budge3Yoko Mitani4William A. Walker5Jeffrey F. Bromaghin6Samantha E. Simmons7Colleen Reichmuth8Daniel P. Costa9Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United StatesDepartment of Biological Sciences, Old Dominion University, Norfolk, VA, United StatesDepartment of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA, United StatesDepartment of Process Engineering and Applied Science, Dalhousie University, Halifax, NS, CanadaField Science Center for Northern Biosphere, Hokkaido University, Hakodate, JapanMarine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic Atmospheric Administration, Seattle, WA, United StatesU.S. Geological Survey, Alaska Science Center, Marine Ecosystems, Anchorage, AK, United StatesMarine Mammal Commission, Bethesda, MD, United StatesInstitute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA, United StatesDepartment of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United StatesUnderstanding the diet of deep-diving predators can provide essential insight to the trophic structure of the mesopelagic ecosystem. Comprehensive population-level diet estimates are exceptionally difficult to obtain for elusive marine predators due to the logistical challenges involved in observing their feeding behavior and collecting samples for traditional stomach content or fecal analyses. We used quantitative fatty acid signature analysis (QFASA) to estimate the diet composition of a wide-ranging mesopelagic predator, the northern elephant seal (Mirounga angustirostris), across five years. To implement QFASA, we first compiled a library of prey fatty acid (FA) profiles from the mesopelagic eastern North Pacific. Given the scarcity of a priori diet data for northern elephant seals, our prey library was necessarily large to encompass the range of potential prey in their foraging habitat. However, statistical constraints limit the number of prey species that can be included in the prey library to the number of dietary FAs in the analysis. Exceeding that limit could produce non-unique diet estimates (i.e., multiple diet estimates fit the data equally well). Consequently, we developed a novel ad-hoc method to identify which prey were unlikely to contribute to diet and could, therefore, be excluded from the final QFASA model. The model results suggest that seals predominantly consumed small mesopelagic fishes, including myctophids (lanternfishes) and bathylagids (deep sea smelts), while non-migrating mesopelagic squids comprised a third of their diet, substantially less than suggested by previous studies. Our results revealed that mesopelagic fishes, particularly energy-rich myctophids, were a critical prey resource, refuting the long-held view that elephant seals are squid specialists.https://www.frontiersin.org/article/10.3389/fmars.2018.00430/fulllipidbiochemical diet analysisQFASAMirounga angustirostrisnorthern elephant sealmesopelagic food web |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Chandra Goetsch Melinda G. Conners Melinda G. Conners Suzanne M. Budge Yoko Mitani William A. Walker Jeffrey F. Bromaghin Samantha E. Simmons Colleen Reichmuth Daniel P. Costa |
spellingShingle |
Chandra Goetsch Melinda G. Conners Melinda G. Conners Suzanne M. Budge Yoko Mitani William A. Walker Jeffrey F. Bromaghin Samantha E. Simmons Colleen Reichmuth Daniel P. Costa Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis Frontiers in Marine Science lipid biochemical diet analysis QFASA Mirounga angustirostris northern elephant seal mesopelagic food web |
author_facet |
Chandra Goetsch Melinda G. Conners Melinda G. Conners Suzanne M. Budge Yoko Mitani William A. Walker Jeffrey F. Bromaghin Samantha E. Simmons Colleen Reichmuth Daniel P. Costa |
author_sort |
Chandra Goetsch |
title |
Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis |
title_short |
Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis |
title_full |
Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis |
title_fullStr |
Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis |
title_full_unstemmed |
Energy-Rich Mesopelagic Fishes Revealed as a Critical Prey Resource for a Deep-Diving Predator Using Quantitative Fatty Acid Signature Analysis |
title_sort |
energy-rich mesopelagic fishes revealed as a critical prey resource for a deep-diving predator using quantitative fatty acid signature analysis |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Marine Science |
issn |
2296-7745 |
publishDate |
2018-11-01 |
description |
Understanding the diet of deep-diving predators can provide essential insight to the trophic structure of the mesopelagic ecosystem. Comprehensive population-level diet estimates are exceptionally difficult to obtain for elusive marine predators due to the logistical challenges involved in observing their feeding behavior and collecting samples for traditional stomach content or fecal analyses. We used quantitative fatty acid signature analysis (QFASA) to estimate the diet composition of a wide-ranging mesopelagic predator, the northern elephant seal (Mirounga angustirostris), across five years. To implement QFASA, we first compiled a library of prey fatty acid (FA) profiles from the mesopelagic eastern North Pacific. Given the scarcity of a priori diet data for northern elephant seals, our prey library was necessarily large to encompass the range of potential prey in their foraging habitat. However, statistical constraints limit the number of prey species that can be included in the prey library to the number of dietary FAs in the analysis. Exceeding that limit could produce non-unique diet estimates (i.e., multiple diet estimates fit the data equally well). Consequently, we developed a novel ad-hoc method to identify which prey were unlikely to contribute to diet and could, therefore, be excluded from the final QFASA model. The model results suggest that seals predominantly consumed small mesopelagic fishes, including myctophids (lanternfishes) and bathylagids (deep sea smelts), while non-migrating mesopelagic squids comprised a third of their diet, substantially less than suggested by previous studies. Our results revealed that mesopelagic fishes, particularly energy-rich myctophids, were a critical prey resource, refuting the long-held view that elephant seals are squid specialists. |
topic |
lipid biochemical diet analysis QFASA Mirounga angustirostris northern elephant seal mesopelagic food web |
url |
https://www.frontiersin.org/article/10.3389/fmars.2018.00430/full |
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