University of Oulu

Tverin M, Esparza-Salas R, Strömberg A, Tang P, Kokkonen I, Herrero A, et al. (2019) Complementary methods assessing short and long-term prey of a marine top predator ‒ Application to the grey seal-fishery conflict in the Baltic Sea. PLoS ONE 14(1): e0208694.

Complementary methods assessing short and long-term prey of a marine top predator : application to the grey seal-fishery conflict in the Baltic Sea

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Author: Tverin, Malin1; Esparza-Salas, Rodrigo2; Strömberg, Annika3;
Organizations: 1Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
2Department of Biology, University of Oulu, Oulu, Finland
3Department of Environmental Research and Monitoring, Swedish Museum of Natural History, Stockholm, Sweden
4Natural Resources Institute, Luke, Helsinki, Finland
5Natural Resources Institute, Luke, Turku, Finland
6Metsähallitus Parks & Wildlife, Savonlinna, Finland
7Estonian Marine Institute, University of Tartu,Tartu, Estonia
8Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
9Department of Aquatic Resources, Swedish University of Agricultural Sciences, Lysekil, Sweden
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.4 MB)
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Language: English
Published: Public Library of Science, 2019
Publish Date: 2019-10-08


The growing grey seal (Halichoerus grypus) population in the Baltic Sea has created conflicts with local fisheries, comparable to similar emerging problems worldwide. Adequate information on the foraging habits is a requirement for responsible management of the seal population. We investigated the applicability of available dietary assessment methods by comparing morphological analysis and DNA metabarcoding of gut contents (short-term diet; n = 129/125 seals, respectively), and tissue chemical markers i.e. fatty acid (FA) profiles of blubber and stable isotopes (SIs) of liver and muscle (mid- or long-term diet; n = 108 seals for the FA and SI markers). The methods provided complementary information. Short-term methods indicated prey species and revealed dietary differences between age groups and areas but for limited time period. In the central Baltic, herring was the main prey, while in the Gulf of Finland percid and cyprinid species together comprised the largest part of the diet. Perch was also an important prey in the western Baltic Proper. The DNA analysis provided firm identification of many prey species, which were neglected or identified only at species group level by morphological analysis. Liver SIs distinguished spatial foraging patterns and identified potentially migrated individuals, whereas blubber FAs distinguished individuals frequently utilizing certain types of prey. Tissue chemical markers of adult males suggested specialized feeding to certain areas and prey, which suggest that these individuals are especially prone to cause economic losses for fisheries. We recommend combined analyses of gut contents and tissue chemical markers as dietary monitoring methodology of aquatic top predators to support an optimal ecosystem-based management.

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Series: PLoS one
ISSN: 1932-6203
ISSN-E: 1932-6203
ISSN-L: 1932-6203
Volume: 14
Issue: 1
Article number: e0208694
DOI: 10.1371/journal.pone.0208694
Type of Publication: A1 Journal article – refereed
Field of Science: 1181 Ecology, evolutionary biology
Funding: The collection and analysis of seal and fish samples was supported by the EU funded Ecoseal project in 2012-13. Additional funding was obtained from Finnish Cultural Foundation (00150994), Otto A. Malms donationsfond (7-5077-44) and Oskar Öflunds stiftelse (2-3496-18).
Copyright information: © 2019 Tverin et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.