Grey seal diet at the southern limit of its European distribution: combining dietary analyses and fatty acid profiles

Ridoux, Vincent; Spitz, Jérôme; Vincent, Cécile; Walton, Michael

doi:10.1017/s002531540705463x

Cited by 25 publications

(34 citation statements)

References 22 publications

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“…Therefore, while this study provides a good indication of which species are the most important contributors to the seals diet in terms of biomass, it is not a true reflection of the overall diet of grey seals in this region. This study has revealed that grey seals using the Great Blasket Island in southwest Ireland are generalist feeders, consistent with studies in other parts of the species' range , Beck et al 2007, Ridoux et al 2007. Previous dietary studies conducted in Ireland in the 1990s indicated that grey seals displayed a wide range of prey preferences, feeding predominantly on demersal species, sand eels, ling and cephalopods (Cronin et al 2010 and references therein).…”

Section: Discussionsupporting

confidence: 86%

Grey seal diet analysis in Ireland highlights the importance of using multiple diagnostic features

Gosch¹,

Hernández-Milian²,

Rogan³

et al. 2014

Aquat. Biol.

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Seals and humans are top predators in many marine ecosystems, often targeting the same food resource. With global declines in fish stocks, competition between these top predators is of increasing interest to scientists and resource managers. To understand and quantify this competition, robust data on the diet of seals are necessary. We present new information on the diet of grey seals Halichoerus grypus from a colony on Great Blasket Island, southwest Ireland, with particular reference to commercially important prey species such as salmonids. Inter-annual variation in diet was investigated based on the recovery and identification of sagittal fish otoliths, bones and cephalopod beaks from faecal samples collected in 2009 and 2010. A total of 939 prey items were recovered, representing a minimum of 41 prey species. Thirty species were identified from otoliths while a further 11 species, including salmonids, were identified from additional diagnostic structures. The diet of grey seals was largely dominated by Gadiformes (21% corrected biomass), particularly Trisopterus spp., which contributed 7% in terms of corrected biomass and 52% by frequency of occurrence, while salmonids comprised over 36% of diet by corrected biomass. Inter-annual variation in sandeel (Ammodytidae) and blue whiting Micromesistius poutassou abundance was apparent, while the former was an important contributor to the diet in terms of corrected biomass (11%). The results support the principle that an 'all structures' approach to pinniped diet estimation can significantly increase the rate of detection for most fish groups, and result in improved estimation of seal diet.

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Section: Discussionsupporting

confidence: 86%

Grey seal diet analysis in Ireland highlights the importance of using multiple diagnostic features

Gosch¹,

Hernández-Milian²,

Rogan³

et al. 2014

Aquat. Biol.

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“…Marine top-predator diets can be estimated using different approaches (for a recent review, see Bowen & Iverson 2013). Long-term analyses are based on the determination of stable carbon and nitrogen isotopes or on fatty acid analysis in the predator tissues (Iverson et al 1997;Das et al 2003;Iverson et al 2004;Ridoux et al 2007;Mèndez-Fernandez et al 2010). These methods integrate the diet of the predators over weeks or months and can provide good estimates of food webs and relationships at high trophic levels.…”

Section: Please Scroll Down For Articlementioning

confidence: 99%

“…These methods integrate the diet of the predators over weeks or months and can provide good estimates of food webs and relationships at high trophic levels. Information on the last few meals can be obtained by direct observation of feeding, stomach content analysis and prey hard part identification in the predator's stomachs and faeces (Bowen & Harrison 1994;Walker et al 1998;Santos & Pierce 2003;Santos et al 2004;De Pierrepont et al 2005;Ridoux et al 2007). In the stomach contents and faeces, fish and cephalopod species are deduced from the identification of otoliths and beaks, respectively, using reference material (Clarke 1986;Härkönen 1986).…”

Section: Please Scroll Down For Articlementioning

confidence: 99%

DNA barcoding for the identification of soft remains of prey in the stomach contents of grey seals (Halichoerus grypus) and harbour porpoises (Phocoena phocoena)

Méheust

Alfonsi

Ménec

et al. 2014

Marine Biology Research

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In recent decades, grey seals (Halichoerus grypus) and harbour porpoises (Phocoena phocoena) have become more numerous along the coasts of Brittany in northwestern France. Their interactions with fisheries are of increasing concern and diet analyses are becoming a requirement to determine the actual overlap between species targeted by fisheries and marine mammal prey. However, as only a few stranded or by-caught animals are available to investigate the diet of these top predators, it is necessary to optimize the results obtained from each animal sampled by increasing the rate of prey species determination in stomach contents. We used a combined analysis of stomach contents, based on prey hard remains and, in parallel, a simple DNA barcoding approach to identify the soft remains. Seven grey seal stomachs and three harbour porpoise stomachs have been analysed. The combined approach, making use of visual observation as well as DNA analysis, increased the identification of prey items by around 32% for grey seal and by 21% for harbour porpoise. Fish species identified include Mediterranean and Atlantic horse mackerel (Trachurus mediterraneus and Trachurus trachurus), Atlantic mackerel (Scomber scombrus), ballan and cuckoo wrasse (Labrus bergylta and Labrus mixtus), European seabass (Dicentrarchus labrax), Atlantic pollock (Pollachius pollachius), European conger (Conger conger) and garfish (Belone belone). One fish species (L. bergylta) was identified only with DNA methods. An area-specific diet for the grey seal in the Iroise Sea, proposed by others in a previous study, seems to be supported.

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“…In recent years, an increasing number of studies have used fatty acid (FA) signature analysis of blubber in seals to examine foraging ecology and diet (Käkelä 1996, Käkelä & Hyvärinen 1998, Walton & Pomeroy 2003, Iverson et al 2004, Arnould et al 2005, Budge et al 2006, Smith & Worthy 2006, Beck et al 2007, Ridoux et al 2007). The underlying principle of FA signature analysis is that the chemical structure of many FAs is not altered as they pass through food webs; therefore, the FA composition in the blubber of a seal is strongly influenced by the FA composition of the diet of the seal.…”

Section: Introductionmentioning

confidence: 99%

Stability of fatty acid composition in seal blubber during long-term storage

Lind¹,

Bäcklin²,

Lundström³

et al. 2012

Mar. Ecol. Prog. Ser.

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This study was performed to evaluate the stability of the fatty acid (FA) composition of blubber from Baltic grey seals Halichoerus grypus archived at −25°C in the Swedish Environmental Specimen Bank (SESB). Possible alterations of FA compositions with storage time and temperature were evaluated. Blubber from 5 seals was kept at + 2°C and at −20°C and sampled for up to 6 mo and 33 mo, respectively. Furthermore, FA profile stability was evaluated in blubber stored in the SESB for 4 and 6 yr. This was done by re-sampling and re-analyzing blubber samples from SESB. In both parts of the study, a principal component analysis was performed on 48 FAs comprising 98 to 99% of the total FAs in blubber of Baltic grey seals. We found no indication of a critically altered FA composition, neither in blubber stored at + 2°C for 6 mo nor in blubber stored at −20°C for 33 mo. The re-analysis of samples stored in SESB for ~4 to 6 yr only differed for a few FAs in some samples. The most remarkable differences were a slight increase in some long-chain unsaturated . As an increase in long-chain polyunsaturated FAs due to storage is highly unlikely, we believe that this is probably more due to the sampling technique than to a critically altered FA composition due to storage. Our results suggest that archived seal blubber may be safely used in retrospective analyses of diet using an FA signature analysis technique.KEY WORDS: Fatty acid composition · Long-term storage · Blubber · Grey seal · Baltic SeaResale or republication not permitted without written consent of the publisher

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Grey seal diet at the southern limit of its European distribution: combining dietary analyses and fatty acid profiles

Cited by 25 publications

References 22 publications

Grey seal diet analysis in Ireland highlights the importance of using multiple diagnostic features

Grey seal diet analysis in Ireland highlights the importance of using multiple diagnostic features

DNA barcoding for the identification of soft remains of prey in the stomach contents of grey seals (Halichoerus grypus) and harbour porpoises (Phocoena phocoena)

Stability of fatty acid composition in seal blubber during long-term storage

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