Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains
The feeding ecology of harbor seals in the outer Oslofjord was investigated during late summer and autumn of 2019 using DNA metabarcoding and morphological hard-parts identification. To evaluate potential competition between seals and fisheries, the annual consumption of fish by harbor seals was est...
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UiT Norges arktiske universitet
2021
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Online Access: | https://hdl.handle.net/10037/22480 |
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ftunivtroemsoe:oai:munin.uit.no:10037/22480 2023-05-15T15:27:24+02:00 Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains Salinger, Audrey 2021-08-15 https://hdl.handle.net/10037/22480 eng eng UiT Norges arktiske universitet UiT The Arctic University of Norway https://hdl.handle.net/10037/22480 Copyright 2021 The Author(s) VDP::Mathematics and natural science: 400::Zoology and botany: 480::Marine biology: 497 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Marinbiologi: 497 VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 harbor seal Phoca vitulina DNA metabarcoding feeding ecology diet composition BIO-3950 Master thesis Mastergradsoppgave 2021 ftunivtroemsoe 2021-09-15T22:53:54Z The feeding ecology of harbor seals in the outer Oslofjord was investigated during late summer and autumn of 2019 using DNA metabarcoding and morphological hard-parts identification. To evaluate potential competition between seals and fisheries, the annual consumption of fish by harbor seals was estimated and compared to the fisheries landings in the outer Oslofjord. Fish species from 16 and 18 families were identified among the feces samples included in the DNA metabarcoding (n = 44) and hard-parts analysis (n = 77), respectively. In total, fish from 25 families were identified as prey. In addition to bony fishes, the DNA metabarcoding revealed that birds and skates may also be components of harbor seal diet in the region. The hard-parts analysis indicated cephalopods were prey as well. The results from molecular and morphological analyses were similar in regard to important prey species, but finer taxonomic resolution of important prey groups was achieved using DNA metabarcoding compared to the more traditional morphological analysis. Additionally, individual scats tended to contain a greater diversity of prey when analyzed by the DNA metabarcoding. In both methods of analysis, gadoid fishes comprised the largest part of the diet. In the hard-parts analysis, the most important prey in terms of relative diet contribution were fish in the unresolved cod/pollack/saithe group (13.0%), followed by Trisopterus spp. (Norway pout/poor cod/bib; 11.2%), Atlantic cod (8.7%), and haddock (8.5%). Similarly, through DNA metabarcoding the most important prey were found to be Atlantic cod (25.5%), haddock, (14.4%) and Trisopterus spp. (12.6%). Thus, the combined approach gives us reason to believe that much of the prey identified as cod/pollack/saithe in the hard-parts analysis may in fact be Atlantic cod. Pleuronectid flatfishes were also common prey in both methods of analysis. The total annual prey consumption by ca. 620 harbor seals in the outer Oslofjord (Færder and Hvaler sub-areas) was estimated as 1009 tons. Our data indicates increased predation on 0-group cod in a year when juvenile cod were exceptionally plentiful. Though prey size estimates showed that seals predate primarily on small fish below minimum allowed landing size for most commercial species, we speculate that harbor seals may expose preferred prey, such as coastal cod, to a “predator pit” phenomenon, and thus question whether seal predation is constraining the recovery of coastal cod in the outer Oslofjord and adjacent areas. Further investigation of diet across multiple seasons in subsequent years is needed to understand how harbor seals regulate prey populations. Master Thesis atlantic cod harbor seal Phoca vitulina University of Tromsø: Munin Open Research Archive Norway |
institution |
Open Polar |
collection |
University of Tromsø: Munin Open Research Archive |
op_collection_id |
ftunivtroemsoe |
language |
English |
topic |
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Marine biology: 497 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Marinbiologi: 497 VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 harbor seal Phoca vitulina DNA metabarcoding feeding ecology diet composition BIO-3950 |
spellingShingle |
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Marine biology: 497 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Marinbiologi: 497 VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 harbor seal Phoca vitulina DNA metabarcoding feeding ecology diet composition BIO-3950 Salinger, Audrey Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
topic_facet |
VDP::Mathematics and natural science: 400::Zoology and botany: 480::Marine biology: 497 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Marinbiologi: 497 VDP::Mathematics and natural science: 400::Zoology and botany: 480::Ecology: 488 VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480::Økologi: 488 harbor seal Phoca vitulina DNA metabarcoding feeding ecology diet composition BIO-3950 |
description |
The feeding ecology of harbor seals in the outer Oslofjord was investigated during late summer and autumn of 2019 using DNA metabarcoding and morphological hard-parts identification. To evaluate potential competition between seals and fisheries, the annual consumption of fish by harbor seals was estimated and compared to the fisheries landings in the outer Oslofjord. Fish species from 16 and 18 families were identified among the feces samples included in the DNA metabarcoding (n = 44) and hard-parts analysis (n = 77), respectively. In total, fish from 25 families were identified as prey. In addition to bony fishes, the DNA metabarcoding revealed that birds and skates may also be components of harbor seal diet in the region. The hard-parts analysis indicated cephalopods were prey as well. The results from molecular and morphological analyses were similar in regard to important prey species, but finer taxonomic resolution of important prey groups was achieved using DNA metabarcoding compared to the more traditional morphological analysis. Additionally, individual scats tended to contain a greater diversity of prey when analyzed by the DNA metabarcoding. In both methods of analysis, gadoid fishes comprised the largest part of the diet. In the hard-parts analysis, the most important prey in terms of relative diet contribution were fish in the unresolved cod/pollack/saithe group (13.0%), followed by Trisopterus spp. (Norway pout/poor cod/bib; 11.2%), Atlantic cod (8.7%), and haddock (8.5%). Similarly, through DNA metabarcoding the most important prey were found to be Atlantic cod (25.5%), haddock, (14.4%) and Trisopterus spp. (12.6%). Thus, the combined approach gives us reason to believe that much of the prey identified as cod/pollack/saithe in the hard-parts analysis may in fact be Atlantic cod. Pleuronectid flatfishes were also common prey in both methods of analysis. The total annual prey consumption by ca. 620 harbor seals in the outer Oslofjord (Færder and Hvaler sub-areas) was estimated as 1009 tons. Our data indicates increased predation on 0-group cod in a year when juvenile cod were exceptionally plentiful. Though prey size estimates showed that seals predate primarily on small fish below minimum allowed landing size for most commercial species, we speculate that harbor seals may expose preferred prey, such as coastal cod, to a “predator pit” phenomenon, and thus question whether seal predation is constraining the recovery of coastal cod in the outer Oslofjord and adjacent areas. Further investigation of diet across multiple seasons in subsequent years is needed to understand how harbor seals regulate prey populations. |
format |
Master Thesis |
author |
Salinger, Audrey |
author_facet |
Salinger, Audrey |
author_sort |
Salinger, Audrey |
title |
Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
title_short |
Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
title_full |
Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
title_fullStr |
Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
title_full_unstemmed |
Feeding ecology of harbor seals (Phoca vitulina) in the outer Oslofjord quantified by DNA metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
title_sort |
feeding ecology of harbor seals (phoca vitulina) in the outer oslofjord quantified by dna metabarcoding of scat soft-matrix and morphological analysis of hard prey remains |
publisher |
UiT Norges arktiske universitet |
publishDate |
2021 |
url |
https://hdl.handle.net/10037/22480 |
geographic |
Norway |
geographic_facet |
Norway |
genre |
atlantic cod harbor seal Phoca vitulina |
genre_facet |
atlantic cod harbor seal Phoca vitulina |
op_relation |
https://hdl.handle.net/10037/22480 |
op_rights |
Copyright 2021 The Author(s) |
_version_ |
1766357843004358656 |