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Prey consumption of Harbour seals (Phoca vitulina) in north western Iceland: Comparing DNA metabarcoding and morphological analyses
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology. Marine and Freshwater Research Institute, Iceland.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Understanding ecological relationships between humans and marine predators is challenging, but crucial for the implementation of sustainable management practices. Comprehensive estimation of pinniped diet is essential for assessing their interaction with commercial fisheries as well as to increase knowledge on ecological interactions and food webs. In Iceland, salmonid fisheries are economically important and harbour seals are often culled in the vicinity of salmon estuaries to prevent potential seal predation on salmonid stocks. There is a lack of information on harbour seal diet, and due to uncertainty of the accuracy of methods traditionally used to estimate harbour seal diet (e.g. hard-part analysis of faeces) it is necessary to improve analysis methods. In this study, we investigated the diet of harbour seals hauling out in an estuary area in north western Iceland between June and September of 2010 and 2011 by DNA analysis of prey in faeces using DNA barcoding. The results were compared to previously published results from morphological analysis. Our results showed that harbour seals mainly consumed sand eels, flatfishes, gadoids, herring and capelin. Species consumed by the seals were at large in agreement with species availability in the area. The results from molecular and morphological analysis were similar in regards of important prey species. However the species diversity was lower in the morphological analysis and 37.5% of the samples included prey items that were unidentifiable in the morphological analysis. Notably, despite salmon, trout and char availability in the study area, neither of the methods found evidence of salmonids in the harbour seal diet. Since the main reason for culling harbour seals in Iceland is to reduce predation on salmonids, the finding that salmonids are not important prey species is important in terms of management implications, especially in the light of a recent severe decline in the Icelandic harbour seal population.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-134796OAI: oai:DiVA.org:su-134796DiVA: diva2:1038541
Available from: 2016-10-19 Created: 2016-10-19 Last updated: 2016-11-22Bibliographically approved
In thesis
1. Ecology, tourism and management of harbour seals (Phoca vitulina)
Open this publication in new window or tab >>Ecology, tourism and management of harbour seals (Phoca vitulina)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In cases where human and wildlife are co-using the same geographical areas and resources, management issues often get complex and stakeholder conflicts are common. The Icelandic harbour seal (Phoca vitulina) population is rapidly decreasing, but direct culling of seals still occurs. At the same time seals are becoming an important resource due to increased interest in wildlife watching. Despite the complicated management situation, the Icelandic harbour seal population is one of the least studied pinniped populations in the world. Mapping the typical haul-out pattern is an important foundation for further studies. In paper I haul-out behaviour of harbour seals was investigated and a seasonal haul-out pattern was detected with the maximum number of seals hauling out during summer. A bimodal distribution curve was found during the summer time, suggesting that pupping period occurs in late May to early June, while moulting occurs in late July to early August. Tidal state, air-temperature and wind-speed affected the haul-out boots. Today, the main reason for culling harbour seals in Iceland is to reduce harbour seal predation on salmonids, despite limited knowledge on the effect of seal predation on salmonid populations and salmon angling. The diet of harbour seals that haul out in the estuary area of Bjargós and Ósar in NW-Iceland was therefore investigated using hard-part (paper II) and DNA metabarcoding analysis (paper III). Both methods showed that the main prey species were sand eels, flatfishes, gadoids, herring and capelin, while salmonids were not an important prey in this area. Based on these results, culling of harbour seals in the area is not likely to have a positive effect on salmonid angling. These results have crucial management implications, especially in the light of the severe decline in the Icelandic harbour seal population. Potential effects of seal watching tourism on the harbour seal population must also be considered in management plans. In paper IV, we investigated the effects of land based seal watching on seal behaviour and found that spatial distribution and vigilance was affected by tourists. Calm tourists behaviour had less effect, meaning that disturbance could be reduced if tourist behaviour is modified. In paper V, this line of investigation was followed by analysing knowledge transfer from academia to the tourist industry and a model was presented where a synergy effect of working interdisciplinary is hypothesised. Finally, in paper VI, the effect of signage on tourist behaviour was studied. Empirical testing showed that teleological information is more effective than ontological in terms of modifying general tourist behaviour. In this thesis, I present new knowledge on behaviour and diet of harbour seals, as well as new empirical findings on tourist behaviour in wildlife tourism settings. Further I explore interdisciplinary management approaches for seal watching tourism. The findings presented in this thesis have an important value within academic research in environmental-, life- and social sciences and the knowledge can be applied in several areas of harbour seal management in Iceland and elsewhere.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2016. 21 p.
Keyword
Harbour seals, Phoca vitulina, ecology, tourism, wildlife, disturbance
National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-134939 (URN)978-91-7649-565-0 (ISBN)978-91-7649-566-7 (ISBN)
Public defence
2016-12-16, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 6: Manuscript.

Available from: 2016-11-23 Created: 2016-10-26 Last updated: 2016-11-28Bibliographically approved

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